An essay on combustion, with a view to a new art of dying and painting : wherein the phlogistic and antiphlogistic hypotheses are proved erroneous

ARMED FORCES MEDICAL1JBR4RY.

Washi^^f D. C.

Surgeon General's Office

PRESENTS

| /La^^

ON

COMBUSTION,

WITH A VIEW TO

A NEW ART

OF

DYING AND PAINTING.

WHEREIN. THE PHLOGISTIC AND ANTIPHLOGISTIC

HYPOTHESES ARV. PROVED

ERRONEOUS.

BY MRS. FULHAME.

THE FIRST AMERICAN EDITION.

PHILADELPHIA. V

PRINTED AND SOLD BY JAMES HUMPHREYS,
Corner of Second and Walnut-streets.

1810.

K

?

ADVERTISEMENT

BY THE AMERICAN EDITOR.

THE interesting contents of the subsequent pages,
by the very ingenious Mrs. Fulhame, are assuredly
deserving of more attention, than they have hitherto
received •, for although published so far back as the
year 1794, little notice has been paid to the numerous
experiments, by which she has opposed the doctrines
of combustion, &c. advanced by the respective advo-
cates of the phlogistic and antiphlogistic theories.
How successfully she has executed this, must be left
to the candid inquirer after Uuth, who, provided
the end be attained, does not stop to consider from
wh.it source it is derived.

.WHPHKtA'T T EXCHANGE

K.L.M.

IV ADVERTISEMENT.

Whether it be that the pride of science, revolted
at the idea of being taught by a female, I know not',
but assuredly, the accomplished author of this essay,
has sufficiently evinced the adequacy of her acquire-
ments, in the promulgation of opinions subversive of
a part of the highly esteemed edifice, raised by the
efforts of Lavoisier and others.

That the work has hitherto remained unknown
in this favoured land, where freedom of inquiry is
so sedulously cherished, is matter of surprise ; espe-
cially when it is known that many years past, the
author was elected an honorary member of the
then-existing chemical society of Philadelphia, a dis-
tinction founded on the merit of this work ; yet the
doctrines here advanced, appear to have been known
to but few individuals, for they have never been
comprised in the lectures on chemistry, which are
given in various parts of the Union — nor, till lately,
has the work been adverted to, in any of the nu-
merous voiumes on the science which annually ap-
pear from the British press. Truth however, at
length appears likely to dissipate those mists, which,
from whatever cause arising, have hitherto oppo-
sed the merited estimation of the author : in some
of the late English treatises, this lady is respect-
fully mentioned ; more particularly by the learned
Dr. Thompson, in the third edition of his invalu-

ADVERTISEMENT. V

able System of Chemistry,* when speaking of the
reduction of the muriate of gold, whilst liquid, by
some of the combustibles, but which decompos : tion
does not happen when dry; he adds "for these very
interesting facts we are indebted to the ingenious
Mrs. Fulhame:" he then proceeds to mention some of
her experiments, and continues "Mrs. Fulhame as-
certained, that this reduction of the gold does not
happen in any case unless the salt be moistened with
water : when perfectly dry, it is not altered. This is
not peculiar to the action of combustibles on metallic
salts : it holds also, as we shall see afterwards, with
respect to the metals. But it is by no means easy to
see what' makes water so indispensably necessary. It
is not, as is commonly suppesed, in order to secure
the fluidity of the mixture : for Mrs. Fulhame has
shewn that ether, though a liquid, has no effect in
reducing gold unless water be present. She accounts
very ingeniously for the phenomena, by supposing
that the water is decomposed. The combustible
combines with its oxygen, while its hydrogen com-
bines with the oxygen of the gold, and reproduces
water. This theory accounts very well for the phe-
nomena ; but it would require some direct proof to
establish it completely."

The concession admitted in the last sentence, from
so celebrated a chemist as Dr. Thompson undoubted-

* Vol. III. p. 127, i3«.

A2

VI ADVERTISEMENT.

ly is, although in some degree counteracted by the
concluding paragraph, cannot but be esteemed a
strong proof of the merit of the opinions here ad-
vanced ; and as a tacit avowal, of the inadequacy of
the usually received explanation, in accounting for
the phenomena under consideration.

Convinced by the forcible arguments and experi-
ments of the decomposition of water being essential
in all the processes here detailed, and considering
the subject much simplified by the exposition given; I
cannot but think the same reasoning would apply in
many other cases, where some of the most active and
energetic agents, are, by the present explanation,
altogether thrown into the back ground. Thus, in
procuring nitrogen gas from muscular flesh by means
of diluted nitric acid, we are told, " that the nitric
acid does not furnish the nitrogen gas is obvious, from
its saturating after its action as large a quantity of
alkali as before ; consequently it could not have suffer-
ed any decomposition."* That this deduction is not
in the true spirit of chemical philosophy, which looks
to the action of affinity, by which decomposition, and
recomposition may at the same time progress, I have
little hesitation in saying; and that the case adverted
to is a compound, and not a simple play of affinity
must be allowed, or we entirely destroy the agency

* Accum's Syst, of Chemistry, Vol. I. p. 047. 2d Eng. Ed.

ADVERTISEMENT. VH

of the most powerful body united, whose presence
is nevertheless admitted to be essential to the process.
If we suppose the nitrogen to be expelled from the
flesh, by the action of the acid, which, with the wa-
ter is also decomposed, we shall have a double por-
tion of oxygen and nitrogen, which may thus com-
bine. The oxygen of the water uniting to the ni-
trogen of the flesh, will produce a fresh supply of
nitric acid, and whilst the nitrogen of the original
acid escapes, its oxygen will unite to the liberated
hydrogen of the decomposed water, to form an equal
quantity. At the conclusion of this process of double
affinity then, we shall have a quantity of new form-
ed acid and water equal to the original, but in which
the original elements, have changed situations. By
this explanation, the acid retains the place of activi-
ty it ought to hold ; and the necessity of its presence,
is hereby maintained.

In like manner it has been said that sulphuric acid
is not decomposed in aiding the decomposition of
water with iron in procuring hydrogen gas, because
it saturates as much alkali as before ; but the same
objections may be made to the validity of this opinion
as to the former ; and the process may be more rea-
sonably explained on the principles of compound af-
finity. When the water is decomposed, its hydrogen
escapes, but the acid is also decomposed, and whilst
the oxygen of the acid oxydates the iron, the oxy-

VIII ABVERTISEMENT.

gen of the water unites with the sulphur to form a
similar quantity of acid, which dissolves the oxyda-
ted iron. It would seem incredible, that in any other
way, either the nitric or sulphuric acids, should be
essential to the processes adverted to ; and from these
and other circumstances, such as, that a metal placed
in dry oxygen gas does not oxydize, which ought to
result, if simple affinity only was requisite ; and by
observing in all the late ingenious experiments of
Mr. Davy, the presence of moisture appears to be
essential in the decomposition of the alkalies, &c.
although he mentions it, as only rendering them con-
ductors, I cannot doubt the justice of the opinions
deduced by Mrs. Fulhame from her numerous and
well conducted experiments : and although it may be
grating to many, to suppose a female capable of suc-
cessfully opposing the opinions of some of our fathers
in science ; yet reflection will serve to satisfy the
mind devoted to truth, that she has certainly thrown
a stumbling block of no small magnitude, in the way
©f sentiments we have been taught to consider as
sacred.

Philadelphia,

February 14th, 1810.

PREFACE.

THE possibility of making cloths of gold, silver,
and other metals by chymical processes, occurred to
me in the year 1780; the project being mentioned
to Doctor Fulhame and some friends, was deemed
improbable. However, after some time, I had the
satisfaction of realizing the idea in some degree by
experiment.

Animated by this small success, I have from time
to time ever since, prosecuted the subject as far as
pecuniary circumstances would permit.

X PREFACE.

I imagined in the beginning, that a few experi-
ments would determine the problem •, but experience
soon convinced me, that a very great number indeed
were necessary, before such an art could be brought
to any tolerable degree of perfection.

A narration of the numerous experiments, which
I made with this view, would far exceed the bounds
I prescribed myself in this essay ; I shall therefore
present the reader only with a few, selecting such as
I judge most interesting, and best adapted to illus-
trate the subject.

Though I was, after some considerable time, able
to make small bits of cloth of gold and silver, yet I
did not think them worthy of public attention ; but
by persevering, I at length succeeded in making
pieces of gold cloth, as large as my finances would
admit.

Some time after this period, I found the invention
was applicable to painting, and would also contribute
to facilitate the study of geography ; for I have ap-
plied it to some maps, the rivers of which I represent-
ed in silver, and the cities in gold. The rivers ap-
pearing as it were in silver streams, have a most
pleasing effect on the sight, and relieve the eye of
that painful search for the course and origin of rivers,

TREFA6E. 311

the minutest branches of which can be splendidly re-
presented in this way.

Notwithstanding this further success, I was dubious
about the propriety of publishing this essay ; I there-
fore shewed some specimens of these metallic stuffs to
persons, whom I thought qualified to judge of them ;
some approved of them very much, and were pleased
to say, that the invention would make an era in the
arts ; others thought it a pretty conceit ; and others
were of opinion that the stuffs had not that splen-
dour or burnished appearance, which could entitle
them to public notice.

The latter opinion had much weight with me ; for
it must be allowed, that the specimens which I shew-
ed them, had not that lustre and polish necessary
for shoulder-knots, lace, spangles, gold muslins, &c.
that some of them had a reddish cast, bordering on
the colour of copper, some a purple, mixed with
gold ; and that some of them were unequal in the die
and seemed stained ; which imperfections were owing
to a partial reduction of the metal in the fibres of
the silk.

But all these imperfections, except the want of
that burnished lustre so necessary for gold lace, span-
gles, &c. I knew I could remedy ; and therefore the

XII PREFACE.

criticism, as far it relates to them, had no great in-
fluence with me.

I am in possession of some pieces, one of which
is about a yard in length, which have scarce any of
these imperfections.

Moreover, that high polish of burnished gold, so
necessary in spangles, lace, &c. would in my opinion,
be a great imperfection in gold stuffs designed for
whole suits ; as a person in such a habit would look
like a gilded statue.

I saw a piece of gold stuff made for the late king
of Spain, which was of a purple colour, with gold
wire shining through it, though rather obscurely,
and it was much admired ; I was so struck with its
beauty, that I attempted to imitate it on a small
bit of white silk ; and succeeded, having produced a
beautiful purple colour, with gold beaming through
it.

Therefore, the want of that burnished appearance
is no objection to this art ; for the paler and cooler,
to a certain degree, the colour of the gold is, the
more lovely do these metallic cloths appear.

I made small bits of gold tiffany, which looked ex-
ceedingly beautiful j the fineness of the thread con-

PREFACE. Xlft

iributing much to that effect-, and, In my opinion,
such webs are inimitable by mechanical means.

Beside, though I am not able to make cloths like
burnished gold, others of greater means and abilities
may ; for we cannot pretend to prescribe any limits
to the perfection, at which chymistry and the art?
may arrive.

However, I must acknowledge, that this unfavour-
able judgment suspended my intention of publishing
this little work, until a celebrated philosopher hap-
pening, some time in October 1793, to see some of
the same pieces, and indeed some of the worst, view-
ed the performance in a very different light.

This illustrious friend of science, not only appro-
ved of the specimens shewn him, but offered to have
a memoir on the subject presented to the Royal So-
ciety : but different incidents dissuaded me from that
mode of publication, and induced me to adopt the
present.

I now no longer hesitated about the propriety of
publishing •, for, every thing considered, I judged,
that though this art could never be established,
which is by no means my opinion, yet the experi-
ments themselvc-j, upon which I attempted to found
B

XIV PREFACE.

It, as they are new, and seem to throw some light oft
the theory of combustion, are not unworthy the at=
tention of chymists.

Those who viewed my performance with a fa*
vourable eye were of opinion, that I should dedicate
this essay to some patron of the arts ; or apply for
his Majesty's royal letters patent, in order to reim-
burse the expense necessarily incurred in this inves-
tigation, an expense so disproportionate to the for-
tune which supported it, that nothing but a certain
fatality and the hope of reward, could induce me
to persevere.

As to patrons, I have Jieard of such beings on the
record of fame, but never saw one ; on the contrary,
it has been my lot to know of many whose malignant
breath, as far as its deadly influence can extend,
never ceases to blast the unsheltered blossoms of
science. And as for a patent, had I even the means
I should perhaps never attempt it ; for if we may
judge of the future by the past, I can safely affirm,
that such an application would be vain.

Thus circumstanced, I published this essay in its
present imperfect state, in order to prevent the fura-
cious attempts of the prowling plagiary, and the insi-
dious pretender to chymistry, from arrogating to

PREFACE. XV

themselves and assuming my invention in plundering
silence ; for there are those, who if they cannot by
chymical, never fail by stratagem and mechanical
means, to deprive industry of the fruits and fame of
her labours.

But the British empire should not forget, that she
owes her power and greatness to commerce ; that she
is, as it were, the hive of the arts, and should not, by
the sulphureous vapour of oppression and neglect,
compel her bees to swarm for protection to foreign
climes, but rather permit them to roam in their native
soil, and allow them, in the winter of life, to sip a
little of the honey of their own industry.

The nation, whose evil genius withholds this pro-
tection, only sounds the trumpet of emigration, and.
must ere long lament her cities deserted, her fields
brown with desolation, and herself the easy prey, and
vile drudge of surrounding greatness.

I first imagined that the proper title of this per-
formance should be, An Essay on the Art of making
Cloths of Gold, Silver, and other Metals, by chymi-
cal processes ; but reflecting on the imperfect state
of the art, and that my experiments related not only
to the reduction, but also to the calcination of me

Xvl PREFACE.

tals and other combustible bodies, I determined to
entitle it, An Essay on Combustion, with a View to a
new Art of Dying and Painting, which includes
every thing the experiments can extend to.

As to the style, I have endeavoured to relate the
experiments in a plain and simple manner, aiming
more at perspicuity than elegance.

I have adopted the French Nomenclature, as the
terms of it are so framed as to prevent circumlocu-
tion, assist the memory, by pointing out the combi-
nation and state of the elements existing in each
compound, as far they are known ; advantages to be
found in no other nomenclature.

However, the English reader must regret, that the
French chymists have not preferred the terms air,
and ammonia, to the less harmonious sounds, gas, and
ammoniac. I took the liberty of writing the latter

ammonia.

I have not related my experiments in the order in
Which they were made, sensible that such a narra-
tion would be tedious, and that a short extract from
them would answer every purpose at present in-
tended.

PREFACE. XVII

The experiments related I have endeavoured to
arrange in such a manner, as mutually to illustrate
each other, by contrasting the successful with those
that failed, thus pointing out a general principle,
which forms a chain through the whole, connects all
the experiments, shews their points of coincidence
and disagreement, and by this means furnishes us
with data, by which I hope the art may be impro-
ved.

This arrangement also facilitates the perusal, and
relieves the mind of that fatiguing attention, which
must necessarily be given to an indigested mass of in-
sulated experiments, that have no clue to connect
them, but has on the other hand its disadvantages ;
for it throws a sameness on the work, incompatible
with that variety which is often so agreeable.

My apparatus consisted chiefly of a few glass ves-
sels for the solution of metals, and the formation of
such elastic fluids as I used. The cheapest and the most
simple of those described by Dr. Priestley answered
my purpose.

Dr. Nooth's machine for combining carbonic acid
with water, is very convenient for making small ex-
periments with some kinds ci gas, as the base of that
machine serves to contain the materials, from which
B2

XVIII PREF4CF.

the gas is obtained ; and the middle glass the cloth
previously dipped in the metallic solution, on which
the experiment is to be made.

The cloth may be suspended in this part of the
machine, by means of a thread and a cork.

As this machine is useful only in experiments on
a very small scale, I sometimes used tall glass cylin-
ders, in which I suspended the subject of the expe-
riment, by means of a thread, a cork, and a bk ^ c * ;
ment.

This cylinder I placed over a vessel containing the
materials, which produced the gas.

It is very convenient to have cylinders of different-
sizes, proportioned to the scale on which the experi-
ments are to be made.

But machinery for confining elastic fluids is not
always necessaryj as most of the experiments may be
performed in the open air.

It may appear presuming to some, that I should en*
gage in pursuits of this nature ; but averse from indo-
lence, and having much leisure, my mind led me to
this mode of amusement, which I found entertaining',

PREFACE. XIX

and will I hope be thought inoffensive by the liberal
and the learned. But censure is perhaps inevitable j
for some are so ignorant, that they grow sullen and
silent, and are chilled with horror at the sight of
any thing that bears the semblance of learning, in
whatever shape it may appear; and should the spectre
appear in the shape of ivomafjy the pangs which tb^y*
suffer are truly dismal.

There are others who suffer the same torture in a
still higher degree ; but by .virtue of an old inspiring
tripod, on which ignorance, servility, or chance, has
placed them, assume a dictatorship in science, and
fancying their rights and prerogatives invaded, swell
with rage, and are suddenly seized with a violent
and irresistible desire of revenge, manifesting itself
by innuendos, nods, whispers, sneers, grins, grimace,
satanic smiles, and witticisms uttered sometimes in
the acute, and sometimes in the nasal obtuse twang,
with an affedted hauteur, and contempt of the spec-
tre ; shrugs, and a variety of other contortions at-
tending.

Sometimes the goblin, which thus agitates them
lurks latent, and nothing is perceived but hollow
murmurs, portending storms : sometimes the lurking
fiend darts with sidelong fury at the devoted object,
which if unarmed falls a victim to the grisly monster.

XX PREFACE.

But happily for human kind, the magic tripod drags
none into its dizzy vortex, but those who are radi-
cally stupid and malicious, who are the beasts of prey
destined to hunt down unprotected genius, to stain
the page of biography, or to rot unnoted in the
grave of oblivion.

Although the surge of deliberate malice be una-
voidable, its force is often spent in froth and bubbles ;
for this little bark of mine has weathered out full
many a storm, and stemmed the boisterous tide ; and
though the ca^(jo be not rich, the dangers which
may hereafter be pourtrayed on votive tablet, may
serve as a beacon to future mariners.

But happen what may, I hope I shall never expe*-
rience such desertion of mind, as not to hold the
helm with becoming fortitude against the storm
raised by ignorance, petulant arrogance, and privi-
leged dulness.

However, were I not encouraged by the judgment
of some friends, and possessed of specimens, to shew
the progress made in the art, I should never perhaps
venture to publish this Essay ; as I am sensible it la-
bours under many imperfections, which inaccuracy
of observation and the drapery of imagination, must
spread over the whole ; imperfections perhaps una-
voidable in such a discussion.

PREFACE. XXI

Finding, the experiments could not be explained
on any theory hitherto advanced, I was led to form
an opinion different from that of M. Lavoisier, and
other great names. Persuaded that we are not to be
deterred from the investigation of truth by any au-
thority however great, and that every opinion must
stand or fall by its own merits, I venture with diffi-
dence to offer mine to the world, willing to relin-
quish it, as soon as a more rational appears,

November $th t 179&.

CONTENTS.

Introduction , . . . 25

chapter i.
Reduction of Metals by Hydrogen Gas . . 37

CHAPTER II.

Reduction of Metals by Phosphorus ... 69

CHAPTER III.

Reduction of Metals by Sulphur .... 103

CHAPTER IV.

Reduction of Metals by Alkaline Sulphure . 121

CHAPTER V.

Reduction of Metals by Sulphurated Hydrogen
Gas 141

CHAPTER VI.

Reduction of Metals by Phosphorated Hydro-
gen Gas j, .... 161

XXIV CONTENTS.

CHAPTER VII.

Reduction of Metals by Charcoal .... 177

CHAPTER VIII.

Reduftion of Metals by Light 199

CHAPTER IX.

Reduction of Metals by Acids 215

CHAPTER X.

■Oxygenation of Combustible Bodies . . . 223

Azote 224

Hydrogen ...... 226

Phosphorus 227

Sulphur 228

Charcoal 229

Metals 232

Light . 231.232

CHAPTER XI.

Conclusion 243

"Nomenclature 247

INTRODUCTION

THOUGH some of the phenomena of combus-
tion were known from the earliest ages, yet no ra-
tional attempt to explain them was made till about
the middle of the 17th century.

Before that period, it was supposed by alchymists
and physicians, that sulphur was the inflammable
principle, on which all the phenomena of combus-
tion depended.

But Beccher perceiving, that sulphur did not ex-
ist in several combustible bodies, asserted it was not
the principle of inflammability ; which he maintain-
ed, was a different substance, common to sulphur
C

26" INTRODUCTION.

and other combustible bodies : this principle he sup-
posed to be of a dry nature, and called it inflamma-
ble earth.

Stahl refined this hypothesis by supposing the in-
flammable earth of Beccher to be pure fire, fixed in
combustible bodies, and constituting an essential
part of them.

According to Stahl, a combustible body, is a com-
pound, containing fixed fire, or phlogiston ,• and com-
bustion is the disengagement of this phlogiston from
a fixed to a free state, attended sometimes with heat
and light : when these phenomena cease, the body
becomes incombustible ; if this calcined body be now
heated with charcoal, or any other inflammable
substance, capable of giving it phlogiston, or fixed,
fire, it returns again to the class of inflammable
bodies.

This hypothesis is so simple and plausible, that,
since the year 1736, it was received, though diffe-
rently modified, all over Europe.

The principal objections to it are, that the exist-
ence of phlogiston cannot be demonstrated; and
that it does not explain, why bodies become heavier
after oxygenation, and lighter after reduction.

INTRODUCTION. 27

M. Lavoisier discovering, that the increase of
weight, which bodies acquire during combustion, is
equal to the weight of the combustible substance,
and that of the vital air employed, denied the exist-
ence of phlogiston, or fixed fire, in combustible bo-
dies ; though he grants the existence of combined
caio. ic in them. He seems then to allow the ex-
istence of phlogiston, but to have changed its name
to that of calorky and denied it the power of prodit»
cing, combustion.

However, after discovering that the increase of
weight, which bodies acquire during combustion,
depended on the quantity of the air absorbed,
he was led to the following beautiful hypothesis,
equally simple as that of Stahl j and if ever any hy-
pothesis deserved the name of theory, surely it i3
that of M. Lavoisier.

According to M. Lavoisier, " ah inflammable bo-
dy is nothing else but a body which has the proper-
ty ot decomposing vital air, and taking the base
from caloric and light; that is to say the oxygene,
which was united to them ; and that a body ceases
to be combustible when its affinity for the oxygene,
is satisfied, or when it is saturated with that prin-
ciple ; but that it becomes again combustible, when
the oxygene has been taken from it by another bo-
dy, which has a stronger affinity with that principle

28 INTRODUCTION.

"When this decomposition of the air is rapid, and
as it were, instantaneous, there is an appearance of
flame, heat, and light ; when on the contrary, the
decomposition is very slow, and quietly made, the
heat and light are scarcely perceptible."*

Thus all the phenomena of oxygenation, which
Stahl ascribed to the disengagement of phlogiston,
M. Lavoisier ascribes to the union of oxygen with
combustible bodies.

And on the other hand, all the phenomena of re-
duction, which Stahl attributed to the union of phlo-
giston to calcined bodies, M. Lavoisier attributes to
the separation of oxygen from the same. Combus-
tion then, according to Stahl, is the transition of
phlogiston from one body to another ; and according
to M. Lavoisier, 'tis nothing but the transition of
oxygen from one substance to another.

Stahl supposed, that the heat and light attending
combustion proceed from the burning body ; but M.
Lavoisier supposes, that the heat and light proceed
principally, and almost entirely from the vital air.

However, this opinion of M. Lavoisier is far from
being established j for Doctor Crawford has shewn,

* Essay on Phlogiston, by Mr. Kirvvan, new edition, p. 2 1
and 16.

INTRODUCTION. 29

that inflammable air contains a much greater quanti-
ty of heat, than vital air does.

It is evident then, that the great advantage which
M. Lavoisier's- hypothesis has over that of Stahl is,
that the former seems to account for the increase and
decrease of weight, which bodies suffer during calci- *
nation and reduction.

Notwithstanding this brilliant discovery, which
seems to account, with such ease, for the increase of
weight, that bodies acquire during combustion, M.
Macquer was of opinion, that M. Lavoisier's hypo-
thesis was insufficient to explode that of Stahl, and
endeavoured to remove the objection urged against
the non-existence of phlogiston, by supposing it to
be light ; and that in every case of combustion, light
and vital air mutually precipitate each other ; so that
according to M. Macquer, when a body is oxygena-
ted, vital air unites to it, and disengages light ; and
on the other hand, when an oxygenated substance is
reduced to its inflammable state, light unites to it and
disengages vital air.

M. Scheel also modified the hypothesis of Stahl,
by supposing that heat, light, and inflammable air,
were compounds of emp) T real, or vital air, and phlo-
giston. Light he thought, contained more phlogis-
ton than heat did ; and inflammable air more than
C2

30 INTRODUCTION.

either ; he farther supposed that these compounds of
vital air and phlogiston were convertible into one an-
other, by the addition or subtraction of phlogiston ;
and that when a metal was reduced by them, they
were decomposed ; their phlogiston uniting to the
substance reduced.

His idea of calcination is, that metals either attract
empyreal air by means of their phlogiston, and thus
form heat, or that they communicate their phlogis-
ton to the air, and attract heat from the fire : and
that, either way, there is empyreal air in the calces,
which makes the overplus of their weight.*

The last modification of Stahl's hypothesis is that
of M. Kirwan, who supposes that inflammable air
exists in a fixed or concrete state in all combustible
bodies, and is the true phlogiston of the ancient chy-
mists ; and as it can be exhibited in the form of air,
its existence is no longer doubtful.

M. Kirwan supposes, that when combustible bo-
dies are calcined, or changed into acids, they com-
bine most commonly with fixed air, formed during-
the operation, by the union of their phlogiston to
vital air ; and sometimes to other substances, and wa-
ter, which is either absorbed in specie, or formed by

* Experiments on Air and Fire. Eng. trans, p. 174,

INTRODUCTION. S I

the union of their phlogiston to vital air, during
calcination.

He supposes, that some of these are restored to
their combustible state by the decomposition of their
fixed air ; some partly by the decomposition of their
fixed air, and partly by its expulsion, and that of the
other foreign bodies they had absorbed ; and lastly,
that some recover their combustibility by the expul-
sion of water, and others possibly by its decomposi-
tion in high degrees of heat. In all these reductions
he supposes a simultaneous reunion of these bodies
to phlogiston, or the inflammable principle.*

Though M. Kirwan's hypothesis seems to aceount
for the increase of weight, which bodies acquire du-
ring combustion, yet he has not proved the existence
of inflammable air in a concrete state, in all combus-
tible bodies ; nor has he shewn, that fixed air is a
compound of inflammable and vital air ; neither has
he proved, that fixed air is the acidifying principle.

All these objections have been made, with great
justice to his hypothesis, by the Antiphlogistians ;
who also object, that M. Kirwan's account of calci-
nation and reduction is complex, and repugnant to
the simplicity of nature ; " for," says M. De Four-

* Essay on Phlogiston, a new edition, p. 38— 166»

32 introduction:

croy, « as the author had admitted three general
species of calcination, it was necessary, that he
should likewise admit three kinds of reduction."*

This criticism is very just; but it will appear, that
the antiphlogistic account of calcination and reduc-
tion is no less complex, erroneous and repugnant to
the simplicity of nature ; for when we consider the
various sources, whence they derive the oxygen;
which oxygenates bodies, and the long list of metal-
lic reducers, which they suppose ; it must be allowed
that if simplicity be a recommendation, their hypo-
thesis is destitute of that advantage.

Thus, according to M. Lavoisier the oxygen which
oxygenates combustible bodies, is sometimes derived
from vital air, sometimes from atmospheric air,
sometimes from acids, sometimes from water, and
sometimes from metallic oxids, &c.

On the other hand, the catalogue of substances
which reduce bodies to their combustible state, is
no less numerous.

« Heat," says M. De Fourcroy, « separates oxy-
gene from some ; one metal takes it from another ;

* Essay on Phlogiston, p. 207;.

INTRODUCTION. 33

hydrogene, or inflammable gas, takes it from most
tnetals, and carbon perhaps from all."*

To this list may be added phosphorus, sulphur,
and compounds of these with hydrogen ; also light
and the electric fluid, &c. as will appear in the se-
quel.

But I shall endeavour to shew, that the hydrogen
of water is the only substance, that restores oxyge-
nated bodies to their combustible state ; and that
water is the only source of the oxygen, which oxy-
genates combustible bodies.

Want of simplicity is not the only defect in Mr.
Lavoisier's hypothesis : for he supposes, that the in-
crease of weight, which bodies acquire during com-
bustion, depends on the absorption of the oxyge-
nous principle alone.

Thus when a bit of phosphorus, sulphur or char*
coal, is burnt in vital air ; the increase of weight,
which these bodies acquire, he attributes entirely
to oxygen, or the base of vital air.

These combustions he explains, by supposing that
the phosphorus, sulphur, and charcoal, decompose

* Es?ay on Phlogiston) p. 205.

3^4- rNTftODUCTIGtf.

oxygen gas, by absorbing its base from caloric and
light, which are set free.

"There is," says M Lavoisier, "a total absorp-
tion of vital air, or rather of the oxygene, which
forms its base in the combustion of phosphorus, and
the weight of the phosphoric acid obtained, is found
to be rigorously equal to the weight of the phospho-
rus, added to that of the vital air employed in its
combustion. The same agreement of weights is ob-
served in the combustion of imflammable gas and
vital air, in the combustion of charcoal,"* &c.

His idea of calcination of metals is the same. -

" We do not," says M. Lavoisier, « affirm that
vital air combines with metals to form metallic cal-
ces, because this manner of enunciating would not
be sufficiently accurate : but we say, when a metal is
heated to a certain temperature, and when its parti-
cles are separated from each other to a certain dis-
tance by heat, and their attraction to each other is
sufficiently diminished, it becomes capable of decom-
posing vital air, from which it seizes the base, namely
oxygene, and sets the other principle, namely calo-
ric, at liberty.

"This explanation of what passes during the cal-
cination is not an hypothesis, but the result of faftst

* Essay on Phlogiston, p. 14,

INTRODUCTION. SS

It is upwards of twelve years, since the proofs have
been laid by one of us, before the eyes of the aca-
demy, and have been verified by a numerous com-
mission. It was then established, that when the cal-
cination of metals is effected beneath an inverted
glass vessel, or in . closed vessels containing known
quantities of air, the air itself is decomposed, and the
weight of the metal becomes augmented by a quan-
tity accurately equal to that of the air absorbed. It
has since been found, that when the operation was
performed in very pure vital air, the whole might be
absorbed.

" No supposition enters into these explanations ;
the whole is proved by weight and measure."*

Hence it is evident, that M. Lavoisier confounds
oxygen with oxygen gas, and considers the latter as
a compound of oxygen, light, and caloric.

But since the dryest oxygen gas contains a large
proportion of water, as Dr. Priestley and M. Kirwan
have shewn ;f and since the whole of the gas, ex-
cept the caloric and light, is absorbed, it necessarily
follows that the increase of weight, which bodies ac-
quire during combustion, depends not only on the
axygen, but also on the water, contained in vital air*

* Essay on Plogiston. p. 13—15.

t Ibid. p. 25. and Philo. Trans. Vol. 78. p. 314.

S6 INTRODUCTION.

Therefore oxids are compounds of combustible
bodies united to ox/gen, and water.

Another great objection to M. Lavoisier's hypo-
thesis is, that he supposes both oxygenation, and re-
duction, effected by a single affinity.

Thus according to him, when iron reduces a sul-
phate of copper, the iron does nothing more than
separate the oxygen from the copper, by its superior
attraction for that principle.

From this view of combustion, grounded on the
most accurate experiments in chymistry, it is ma-
nifest that the antiphlogistic hypothesis does not
account fully for the increase of weight, which bodies
acquire during combustion •, and consequently, that
it cannot be admitted as a just theory.

COMBUSTION,

Xc. 8Cc,

CHAPTER I.

REDUCTION OF METALS

BY

HYDROGEN GAS.

AS Hydrogen, or the base of inflammable air,
seems to aft an important part in the following ex-
periments, and is, according to some chymists, pure
phlogiston itself; I have therefore assigned the first
chapter in this essay to hydrogen gas, this being the
most simple form, in which hydrogen has hitherto
been obtained.

D

58 REDUCTIONS BY

But I had not the means of procuring this gas free
of carbon, and other impurities, that it dissolves
and elevates during its formation ; or of excluding
atmospheric air, which circumstances, I am sensible,
must, in some measure, influence the result ; as it
cannot be supposed, that these extraneous bodies
would remain inactive during the process of reduc-
tion. However, as such exactness is not in the power
of every experimenter, I was under a necessity of
using hydrogen gas, with the disadvantages here
mentioned.

Though most of the experiments in this essay were
made on a variety of white and coloured silks, I
shall relate only those made on the former, as it ex-
hibits the changes produced more distinctly, and con-
tains less foreign matter to modify the result of ex-
periment ; and, for brevity's sake, I shall use the
term -silk, by which white silk is always designed.

EXPERIMENT I.

GOLD.

.1 poured a quantity of sulphuric ether on a solu-
tion of gold in nitro muriatic acid, and, by this
means, obtained a solution of gold in ether, which I
separated from the acid.

HYDROGEN GAS. 39

In this ethereal solution of gold, I dipped a piece
of silk •, after it was taken out, and the ether evapo-
rated, it was suspended in a tall glass cylinder, placed
over a vessel, containing a mixture of diluted sul-
phuric acid, and iron filings.

The silk thus exposed to a rapid current of hy-
drogen gas acquired, after some time, a purple co-
lour, and a large spangle of gold, of an irregular
figure, appeared on the upper end of the silk, and
looked very brilliant.

The silk was kept exposed to the gas about four
months, and frequently observed, but no other re-
markable change was perceived, except that the pur-
ple colour became more intense : the experiment was
now discontinued ; and on taking out the silk, and
ex-.i 'inning it in the light of the sun, particles of re-
duced gold were observed ; but they were very small,
and by no means so brilliant, as that, which first ap-
peared.

During the experiment, fresh quantities of mate-
rials for supplying hydrogen gas were occasionally
added.

From the brilliant spangle of reduced gold obser*-
ved in this experiment, I concluded, that there was
a sufficient quantity of the metal in the fibres of the
silk, could it be reduced.

40 REDUCTIONS BT

This spot of reduced gold was very permanent,
ana adhered firmly to the silk.

EXPERIMENT IJ.

GOLD.

In order to determine, whether a solution of gold
in ether, or one in water, were best adapted to the
object of these experiments; I evaporated to dryness
a solution of gold in nitro-muriatic acid, and dissol-
ved the salt in distilled water: in this solution, I im-
mersed a piece of silk, which, after it was dried in
the air, was suspended in a glass cylinder, like the
former piece, and exposed to the action of hydrogen
out two months.

The silk after some time assumed a purple colour,
and five or six specks of reduced gold, of the size of
pin heads, and one much larger, were observed.
Examining the silk in the sun-bean;s, I perceived the
whole of it spangled with minute particles of redu-
ced gold.

After many experiments with these two solutions
of gold, I was led to conclude, that the solution in
water answered best.

HYDROGEN GAS. 41

EXPERIMENT III.

SILVER.

Having dissolved some pure silver in diluted nitric
acid, and evaporated some of the water by a gentle
heat, I placed it in the dark to crystallize The
crystals were separated from the solution, and dissol-
ved in distilled water; to one measure of this solu-
tion, which was saturated with the nitrate of silver,
ten or twelve measures of distilled water were added.

In this diluted solution, a piece of silk was dipped;
after it was taken out, it was dried at the fire : the
silk dried in this manner, retained its white colour ;
whereas, were it dried gradually in the air; and es-
pecially, were the light considerable, its white colour
would be changed to a reddish brown, more or less
intense, according to the quantity of light present.

Some kinds of silk, on being immersed in a solu-
tion of nitrate of silver, have some of their threads
immediately coloured brown ; but I often got white
silk, which would retain its pure white eolour, if dried
at the fire, or in the dark.

The piece of silk dried, as above, was suspended
:n the middle glass of Dr. Nooth's machine; and in--
D 2

42

REDUCTIONS Li-

tO the lower glass were introduced a diluted solution
ef sulphuric acid, and some small iron nails.

The machine was now placed in a dark closet, to
exclude the action of light; after some time, the silk,
thus exposed to hydrogen gas, put on a light brown
colour, which gradually became deeper, until it was
changed to a disagreeable black, with some mixture
of brown : then very small particles of reduced silver
began to appear, which increased by degrees, in
number, and brightness.

The experiment was continued four months ; af-
ter which time, the silk was taken out of the ma-
chine : it had a gray metallic appearance, intermixed
with a considerable tinge of brown.

This experiment was repeated on another piece of
silk, every circumstance being the same, except that
a quantity of water was put in the middle glass of the
machine, over which the silk was suspended ; the
intention of interposing the water in this experiment
was to purify the gas.

The appearances were much the same, as in the
last experiment ; except that the silk became black
sooner; and that some spangles of the silver were
larger, and better reduced.

The specks of reduced silver were permanent, and
adhered firmly to the silk,

HYDROGEN GAS, *3

EXPERIMENT IV.

LEAD.

In a solution of acetite of lead in distilled water I
dipped a piece of siik, and dried it in the air ; it was
then suspended over a quantity of water in Dr.
Nooth's machine, and exposed to hydrogen gas about
three months.

The appearances were much the same as in the
last experiment, except thatthe silk was not so black:
the particles of reduced lead resembled silver.

Similar experiments were made in this machine on
bits of silk imbued with a solution of nitro-muriate of
gold in water ; but the appearances being much the
same as those mentioned in the first and second ex-
periments, it is unnecessary to repeat them here.

It is much easier to imagine, than express my
anxiety, to discover the cause of the brilliant specks
of reduced gold and silver, with which the pieces of
silk in these experiments were sometimes spangled ;
concluding, that were the cause ascertained, it would
be a considerable step towards accomplishing the ob-
ject in view.

4t> REDUCTIONS liT

But many and diversified were the experiments I
made before the circumstance, on which the spangle3
depended, was perceived.

At length, I found it depended on the presence of
moisture ; and that the spangles of reduced metal
were owing to small drops of water carried up by
the elastic fluid, and deposited on the silk.

The experiments, which led to this conclusion,
shall be related in their proper places. I shall now
proceed to recite the remainder of the experiments
in this essay, conformable to the plan laid down in
the preface, premising an occurrence observed in the
course of them.

I sometimes found, that the production of hydro-
gen gas from a mixture of acid, water, and iron nails,
would unexpectedly stop, which induced me to add
more acid •, this not succeeding, I added more wa-
ter j but still no gas was formed : the proportions
of acid and water were varied without effect. Think-
ing the mixture of acid and water unfit for the pur-
pose, I poured it off, and repeatedly washed and
agitated the nails with more water, which was also
poured off; but happening inadvertently to add
some of the mixture of acid and water, which I had
before poured off as unfit for use, I was surprised to
find the gas produced with great rapidity.

HYDROGEN GAS. 45

Reflecting on the cause of this odd circumstance,
I concluded that it depended on a crust of super-
oxygenated iron, formed on the surface of the nails,
which defended them from the action of the water
and acid, and that this crust was removed by the
agitation and washing, which enabled the diluted
acid to act again on the iron.

EXPERIMENT V.

GOLD.

I immersed a bit of silk in a solution of nitro-
muriate of gold in distilled water, and dried it in the
air ; it was then placed over a cylindrical glass vessel,
containing a mixture of diluted sulphuric acid and
iron nails, for about half an hour i but no reduction
of the metal could be observed.

I dipped another bit of silk in the same solution
of gold, and exposed it, while wet to the same cur-
rent of hydrogen gas, and instantly signs of reduction
appeared ; for the yellow colour, which the solution
imparts to silk, began to change to a green, and very
soon a film of reduced gold glittered on the surface
opposed to the gas : shortly after, a beautiful blue
spot, fringed with orange and purple, was formed
on the middle of the silk. During the experiment,
which lasted about half an hour, the silk was kept
constantly wet with distilled water.

$6 REDUCTIONS BY

When experiments are made with this preparation
of gold, it is necessary to evaporate the solution to
dryness, before the salt be dissolved in the water; as
an excess of acid prevents the reduction in a great
measure. Solutions of gold in these experiments do
not admit of being so largely diluted, as solutions of
silver, and other metals do.

EXPERIMENT VI.

SILVER.

I immersed a piece of silk in a solution of nitrate
of silver, and dried it in a dark place ; it was then
exposed to a current of hydrogen gas about twenty
minutes ; but no reduced silver appeared, the only
change observable was a brown stain.

I immersed another bit of the same silk in the
same solution of silver, and having exposed it, while
wet, to a stream of hydrogen gas, I soon observed
evident signs of reduction ; the white colour of the
silk was changed to a brown, which became gradual-
ly more intense; and the surface of the silk, oppo-
sed to the gas, was coated with reduced silver : va-
rious colours, as blue, purple, red, orange, and yel-
low, attended the reduction. These colours often
change, and are succeeded by others in the progress
of the reduction. The threads of the silk look like

HYDROGEN GAS. 47

silver wire, tarnished in some parts, but of great lus-
tre in others.

The silk was kept wet with distilled water during
the experiment. When the silk happened to be too
much wetted, the under surface opposed to the gas
was often covered with scales of a dull blue colour :
these, after the silk dries, may be brushed off, and
another coat of reduced silver, which adheres firm-
ly, but has no considerable brightness, is left behind.

These experiments on the reduction of gold, and
silver, were often repeated with nearly the same re-
sult.

EXPERIMENT VII.

SILVER.

Thinking some other preparation of silver might
answer better than a nitrate, I precipitated some of
the latter with a solution of muriate of soda, and
poured the whole on a filter ; the precipitate was well
washed with distilled water, and dissolved in ammo-
nia. In this solution I immersed a piece of silk, and
dried it in the air; and having exposed it to the action
of hydrogen gas, I could perceive no signs of reduc-
tion, except a faint brown colour.

i'8 REDUCTIONS BY

I dipped another bit of silk in the same solution of
silver, and in order to determine if water had the
power of promoting the reduction of the silver in
this preparation, as it had in the former experiments,
I exposed the silk, while wet, to the same current of
hydrogen gas ; and in a few seconds the metallic lus-
tre was evident on the surface opposed to the current.
After some little time, a blue speck and a faint trace
of yellow appeared, but soon vanished.

This preparation of silver does not stain white silk
so much as a nitrate does; the reduced silver was in-
deed very brilliant, but soon grew dull, and disap-
peared ; a brown stain only remaining ; so that it
seems rather inferior to nitrate of silver, which also,
after reduction, tarnishes, grows dull, and often dis-
appears ; but sometimes part of it remains perma-
nently reduced.

EXPERIMENT VIII.

PLATINA.

With much difficulty I procured a small quantity
of the ore of platina, and dissolved it in nitro muri-
atic acid. The solution was evaporated to dryness,
and the salt was then dissolved in distilled water.

A bit of silk was dipped in part of this solution,
and dried in the air ; it was then exposed to a brisk

HYDROGEN GAS. 49

current of hydrogen gas about twenty minutes, but
no signs of reduction appeared.

Another bit of silk was immersed in the solutioi
of platina, and exposed, while wet, to the same cur-
rent of hydrogen gas ; in five or six minutes the pla-
tina was reduced, exhibiting a livid white metallic
appearance on the surface of the silk opposed to the
current. No colours attended the reduction. This
solution imparts a yellowish brown colour to silk.

After some time, the whole of the metallic lustre
disappeared, in proportion as the silk became dry.

The solution of platina requires more time, and a
stronger current of hydrogen gas for its reduction)
than solutions of silver and gold do.

EXPERIMENT IX.

MERCURY.

I immersed a bit of silk in a solution of oxygena-
ted muriate of mercury in distilled water, and dried
it in the air : it was then exposed to a stream of hy-
drogen gas ; but underwent no visible change.

I dipped another bit of silk in the same solution
of mercury, and exposed it, while wet, to the same
E

50 REDUCTIONS BY

current of gas ; the metal was soon reduced in a beau-
tiful manner, and resembled silver.

The reduction began suddenly, with scarce any ap-
pearance of previous stain ; some very faint, but at
the same time transparent colours attended it : the
most remarkable of these were a light orange, with
a fringe of blue, and a yellow verging on a faint-
green. These colours soon disappeared.

After the silk was turned, I observed, that its tex-
ture was, in some parts, concealed by a thin film,
which, as the reduction proceeded, was perceived to
dart along the threads of the silk, gilding them in a
beautiful manner, and exhibiting the texture very
distinctly.

After some time, the mercury seemed to disappear,
so as to render it doubtful whether any of it remain-
ed in the silk •, but shaking it in the sun beams, I
perceived bright atoms fly off; and rubbing the silk
on a bit of blue paper, I observed shining metallic
particles, which seemed to have lost their affinity of
aggregation, for they did not unite.

One remarkable difference between this prepara-
tion of mercury and nitrate of silver, is, that no black
or brown stain preceded, attended, or followed, the
reduction of the mercury.

HYDROGEN GAS. 51

Mr. Scheele reduced a prussiate of mercury, di»
solved in water, by adding iron filings and a sma^
quantity of sulphuric acid to the solution.*

EXPERIMENT X.

COPPER.

A piece of silk was immersed in a solution of sul-
phate of copper, then taken out, and dried, and ex-
posed for a considerable time to a brisk current of
hydrogen gas-, but no signs of reduction could be
perceived.

Another bit of silk was dipped in the same solu-
tion of copper, and exposed, while wet, to the same
tapid current of hydrogen gas •, the appearances were
the following.

After a minute, or two, the silk assumed a faint
brown colour, and, on the surface opposed to the gas,
a white metallic pellicle appeared, which vanished in
proportion as the silk became dry : wetting the silk
again, I perceived a similar pellicle appear, which al-
so vanished, as soon as the silk dried. If the silk be
kept constantly wet, the brown colour becomes much
more intense, attended with a very slight tinge of

* Scheele, p. 161, French translation. This is the usual
process for obtaining the Trussic acid.

52 REDUCTIONS BY

red. The margins of the silk projefting beyond tlie
verge of the glass cylinder, and therefore not expo-
sed to the current of the gas, retained the blue co-
lour, which the solution imparts.

In some of these white metallic pellicles there ap-
peared a faint brown inclining to yellow, which re-
flected the light, though obscurely.

After the silk dried, nothing remained, but a brown
stain.

EXPERIMENT XI.

LEAD.

A piece of silk was immersed in a solution of ace-
tite cf lead in distilled water ; it was then dried, and
exposed for some time to a stream of hydrogen gas;
but underwent no perceptible change.

Another bit of silk was dipped in the same solu-
tion of lead, and exposed, while wet, to the same
current of hydrogen gas; in a second, or two, the
surface of the siik, opposed to the current, was coat-
ed with reduced lead, which looked like silver.

The reduction was accompanied with a brown
stain, but by no means so intense as that, which at-
tends the reduction of nutate of silver.

HYDROGEN GAS. 53

The other side of the silk was opposed to the cur-
rent of hydrogen gas, and soon acquired a metallic
coat of the same brilliant appearance ; exhibiting the
texture of the silk, in a very striking manner.

It is remarkable, that lead exhibits no colour, but
a light brown, during its reduction ; whereas gold,
silver, and mercury, display a great variety of co-
lours, especially the two former.

After some time the lead reduced in this manner
loses its metallic splendour considerably •, and that in
proportion as the silk dries.

EXPERIMENT XII.

TIN.

f dissolved some crystals of muriate of tin in dis-
tilled water ; dipped a bit of silk in the solution ; and
dried it in the air : it was then exposed to a stream
of hydrogen gas a considerable time ; but no change
or appearance of reduction, could be observed.

Another bit of silk was immersed in the same so-
lution of tin, and exposed, while wet, to the same
current of gas ; after some little time, the reduction
commenced, attended with a great variety of beauti-
E 2

fS4j REDUCTIONS BY

burs ; as red, yellow, orange, green, and blue,
variously intermixed.

The reduced tin disappears along with these co-
lours, as the silk dries ; nothing remaining but a
feuille-morte colour.

The same solution of tin was also reduced by hy-
drogen gas, obtained from tin, and the muriatic acid.

These experiments do not succeed well with mu-
riate of tin containing an excess of acid.

EXPERIMENT XIII.

ARSENIC.

A muriate of arsenic, which was prepared by di-
gesting white oxid of arsenic in muriatic acid, and
continuing the heat, till most of the acid evaporated,
and left behind a soft mass of the consistence of tar,
was dissolved in distilled water.

In this solution a bit of silk was immersed, and
dried in the air : it was exposed to a brisk stream of
hydrogen gas, obtained from zinc, and muriatic
acid j but no reduction took place.

Another bit of silk was dipped in the same solu-
tion, and exposed, while wet, to the same current

HYDROGEN GAS. Sf&

of hydrogen gas •, and instantly, the surface of the
silk, opposed to the gas, was covered with a bright
coat of reduced arsenic, accompanied with a yellow
stain. In a short time the metallic lustre vanished j
and nothing remained but the yellow stain.

M. Pelletier restored the acid of arsenic to its me-
tallic state, by passing hydrogen gas through a solu-
tion of that acid, in twice its weight of water.*

EXPERIMENT XIV.

BISMUTH.

A bit of silk, which was immersed in a solution of
nitrate of Bismuth in distilled water, and exposed dry
to hydrogen gas, obtained from zinc, and muriatic
acid, underwent no visible change.

Another bit of silk was dipped in the same solution
of bismuth, and placed over a languid stream of hy-
drogen gas ; the bismuth was soon restored to its
metallic form, on the surface of the silk opposed to
the elastic fluid. The reduction was attended with
a reddish brown stain, intermixed with a tinge of
Yiolet.

* Roz. Journ. Feb, \j%t+

REDUCTIONS 34"
EXPERIMENT XV.

ANTIMONY.

A bit of silk was immersed in a solution of tar-
trite of antimony in distilled water j and dried in the
air. It was then exposed to hydrogen gas, obtained
from zinc, and muriatic acid ; but suffered no visi-
ble alteration.

Another bit of silk, which was dipped in the same
solution of antimony, was ex-posed wet to a weak
stream of the gas; and, in a short time, the metallic
lustre appeared, accompanied by a light yellow
colour.

EXPERIMENT XVI.

IRON.

A bit of silk, which was immersed in a largely di-
luted solution of sulphate of iron, and dried in the
air, was exposed to a strong current of hydrogen gas,
obtained from iron nails and diluted sulphuric acid j
but no visible change was produced on the silk.

Another bit of silk was dipped in the same solution
of iron, and placed wet over the same stream of hy-

HYDROGEN GAS. &_

drogen gas ; but no reduced iron could be percei-
ved. The silk was then immersed in a glass of clear
water, and transferred a very minute metallic film to
the surface of that fluid.

This experiment was repeated, with a rapid cur-
rent of hydrogen gas, obtained from zinc, and muri-
atic acid i and, in about a minute, small films of re-
duced iron were visible on the surface of the silk,
opposed to the gas.

The silk was then immersed in water, and trans-
ferred to its surface a large metallic pellicle; parts of
which were very brilliant ; but other parts were dull,
and much more imperfeclly reduced.

EXPERIMENT XVII.

ZINC.

A bit of silk, which was dipped in a muriate of
Zinc largely diluted with water, and dried in the air,
was exposed to a rapid current of hydrogen gas, ob-
tained from zinc, and muriatic acid -, but suffered no
visible alteration.

Another piece of silk was immersed in the same
solution of zinc, and exposed, while wet, to the same
rapid current of hydrogen gas : in about half a mi-
nute, the metal was reduced in a verv evident man-

58 REDUCTIONS BY

ner, on part of the silk. The silk was then dipped in
a glass of clear water, and transferred a bright metal-
lic film to its surface.

As these reductions of iron, and zinc, by hydro-
gen, are contrary to M. Lavoisier's table of the affini-
ties of the oxygenous principle ; I began to suspect,
that the films, which were so evident, both on the
silk, and the water, might be abraded, or torn from
the zinc, by the muriatic acid; and elevated, and
deposited on the silk by the gas.

In order to remove this doubt, I dipped a bit of
the same silk in distilled water ; and exposed it,
while wet, to the same current of hydrogen gas, but
nothing metallic could be seen on the silk ; nor did
it when immersed in water transfer a film, or the
smallest appearance of a metal, to the surface of that
fluid : and therefore, there can be no doubt of the
reality of these 1 eductions.

Dr. Priestley restored iron, and lead, to their me-
tallic state, by heating their oxids with a burning
glass in hydrogen gas.

These experiments point out an error in M. Berg-
man's table of elective attra&ions in the humid way ;
for he assigned the last place in that table to phlogis-
ton, which he considered as the base of inflammable

HYDROGEN GAS. 59

air ; because he was unacquainted with any metallic
reductions effected by hydrogen in the humid way.*

Having found, that water promoted, and accelera-
ted these reductions in a very remarkable manner ;
I was curious to know, if alcohol, and ether, would
produce the same effect. With this view, 1 eva-
porated a solution of gold in nitro-muriatic acid to
dryness ; when the vessel cooled, some alcohol was
poured on to dissolve the salt ; and immediately the
vessel containing the salt, became so hot, that it could
be scarcely endured by the hand; and diffused a fra-
grant smell, like that of ether, which, no doubt, was
a species of that fluid.

EXPERIMENT XVIIi.

GOLD.

In this solution of gold in alcohol, a bit of silk was
dipped, and exposed to a stream of hydrogen gas, ob-
tained from diluted sulphuric acid, and iron nails ;
and kept wet with alcohol : in about two minutes,
the silk began to assume a brown colour, and white
metallic films appeared on some parts of the surface
opposed to the gas ; some of these disappeared in a
short time ; and were succeeded by a few very small
spangles of the proper colour of gold. These also

• Electire Attractions, English Translation, p. 8-.

GO REDUCTIONS BY

soon vanished; and nothing remained but a disagree-
able brown stain, intermixed with specks of a dull
blue.

I sometimes found, on repeating this experiment,
that no yellow films or spangles appeared ; and am
persuaded, that their appearance, and that of the
white pellicles also, depends on the presence of wa-
ter, contained in the alcohol, or the gas, and depo-
rted on the silk.

EXPERIMENT XIX.

GOLD.

A bit of silk was immersed in a solution of gold in
ether, and exposed to a stream of hydrogen gas, and
kept wet with ether. The silk underwent no altera-
tion for a few minutes ; at length, it began to assume
a faint brown colour, but no white, or yellow films
appeared.

If this experiment be continued till the silk collects
a sufficient quantity of water from the gas, some films
will appear.

HYDROGEN GAS. 6i

EXPERIMENT XX.

SILVER.

I procured some nitrate of silver, which had been
fused in order to expel as much of its water as possi-
ble ; and dissolved it in alcohol. I immersed a bit
of silk in this solution, and exposed it to a stream of
hydrogen gas, and kept it wet with alcohol : in a few
seconds, the silk assumed a brown colour, which gra-
dually became more intense: but no reduced silver
appeared for several minutes ; at length, a few metal-
lic films appeared on part of the surface opposed to
the gas.

EXPERIMENT XXI.

MERCURY.

A bit of silk was dipped in a solution of oxygena-
ted muriate of mercury, and dried ; it was then ex-
posed to hydrogen gas about ten or fifteen minutes,
and kept constantly wet with alcohol. The silk, du-
ring the first minutes, suffered no perceptible altera-
tion : at length, a few small films were visible on the
side of the silk opposed to the current.
F

62 REDUCTIONS BY

EXPERIMENT XXTI.

LEAD.

A bit of eilk which was immersed in a solution of
acetite of lead, and dried, was exposed'about fifteen
minutes to a stream of the gas ; and kept constantly
wet with alcohol; but suffered no visible change; ex-
cept that a very minute film was reduced on one of
its margins, which did not project beyond the verge
of the glass vessel on which it was placed.

When we compare these experiments with those,
in which wzter was used, to wet the silk, 'tis evident,
that alcohol, and ether, do not promote the reduc-
tion of metals, as water does ; and that the few films,
which appear, when the silk is kept wet with ether
or alcohol, depend entirely on water collected from
the gas, or deposited by them on the silk during their
evaporation.*

In order to compare the effects of hydrogen gas,
obtained from water, iron nails, and muriatic acid,
with that, procured from the same materials, by
means of the sulphuric ; I made some experiments
on gold, silver, mercury, and lead, in the same man-

* Or, which is most probable, from water contained in the
alcohol, owing to the great difficulty of procuring it perfecUy
rectified. Am. Ed.

HYDROGEN GAS. 63

ner, as the preceding ; and the principal difference
was, that the colours produced in all the pieces of
silk, except that, which was dipped in acetite of lead,
were much brighter, and more beautiful, than any
produced, when the sulphuric acid was used.

The reduction of the lead was accompanied with
its usual brown colour.

On the upper surface of a bit of silk, which was
dipped in a solution of gold, a green colour instantly
appeared ; and soon changed to a deep olive, in pro-
portion as the reduction advanced : now examining
the under surface, I saw it coated with a bright film
of reduced gold, in the middle of which a blue span-
gle, mixed with purple, soon began to appear : I
then moistened the upper surface of the silk with
water ; and in a few seconds, it also was coated with
reduced gold.

The blue on the other side of the silk became
much more intense : the piece was now turned; and
on each colour I let fall a drop of water: the drop
on the blue had a blue film, the drop on the purple,
had a purple film, and the drop on the yellow, a film
of reduced gold.

After some time, these drops of water evaporated,
and the films came again in contact with the silk :
some parts of which were left bare, as generally hap-
pens, when too much water is applied.

§4> REDUCTIONS BY

On the under surface of a bit of silk, which was
immersed in a solution of nitrate of silver in water,
a coat of reduced metal was formed, with various co-
lours, as green, blue, orange, and yellow, the beau-
ty and brightness of which were remarkable.

In some time a muriate of silver is formed in the
fibres of the silk, which 01 exposure to light becomes
of a bluish black colour ; but the whole of the silver
does not undergo this change, for part of it remains
in its metallic state. The colours remain a conside-
rable time, if the silk be removed from the gas be-
fore this muriate is formed.

Hence it appears, that hydrogen gas should not be
prepared wirh an acid, which forms an insoluble
compound with the metal to be reduced.

I also found, that hydrogen gas produces different
effects not only according to the difference of the
acid, but also according to the difference of the me-
tal employed to obtain it ; for this gas procured from
zinc or tin, and muriatic acid, did net restore gold
to its proper metallic lustre j but formed on the silk,
a white metalline coat like silver.

The experiments related in this chapter indicate
the following conclusions.

HYDROGEN GAS. 65

1 . Hydrogen is capable of reducing the metals in
the ordinary temperature of the atmosphere.

2. Water promotes and accelerates these reduc-
tions, in a very remarkable manner.

3. Ether and alcohol do not promote these redue--
tions, without the aid of water.

4. A variety of colours accompanies these reduc-
tions, similar to what appears, during the calcination
of metals by heat and air j and depends on the same
cause ; viz. the quantity of oxygen combined with
the metal.

These colours have not been observed hitherto ;
nor indeed could they, as the metals were reduced in
close vessels, and in high degrees of heat.

5. These reductions often disappear.

This is commonly owing to an imperfect and par-
tial reduction of the metal ; for the acid and water
remaining in that part of the metallic solution, not
reduced, re-calcines these delicate films ; sometimes
the disappearance of the metallic lustre depends on
the nature of the metal itself; thus arsenic, lea !. sil-
ver, &c. suffer some degree of calcination by water
and atmospheric air.
F 2

66 REDUCTIONS BY

Messrs. Bergman and Keir relate instances, in which
silver after being precipitated in its metallic state, was
re-calcined, and disappeared.

I first imagined, that water promoted these reduc-
tions by minutely dividing the particles of the metal-
lic salt, and by condensing the gas, and bringing its
hydrogen, and the metallic oxide, within the sphere
of attraction ; the hydrogen either uniting to the me-
tallic earth and reducing it, as the Phlogistians sup-
pose j or uniting with, and separating the oxygen of
the metal, and thus restoring it to the metallic form,
as the Antiphlogistians maintain.

But it is evident from the experiments related, that
water does not promote these reductions solely, by
minutely dividing the particles of the metallic salt ;
for were this the case, ether and alcohol should pro-
mote the reduction of the metallic salts, which they
dissolve, since they divide their particles as minutely
as water can.

Since then metallic solutions in ether, and alcohol,
cannot be reduced by hydrogen gas ; it follows that
the above supposition concerning the mode of agency
of water does not account for the reduction of metals
in this way.

And indeed were it true that hydrogen condensed
by water reduced metals in the manner above men-

HYDROGEN C 67

tioned, it would follow, that the reduction was ef-
fected by a single affinity, which cannot be admitted;
1st. because the existence of a single affinity in such
cases has not been proved ; 2dly, because a double
affinity always takes place in preference to a single
affinity, which is demonstrated by the following facts,
transcribed from the works of Mr. Kirwan.

"If a solution of silver in the nitrous acid be
" thrown into a mixed solution of fixed alkali and
w common salt, the silver will be precipitated by the
«« marine acid of the common salt, and not by the
** free alkali, contained in the liquor : for a luna cor-
«* nea is found."*

" I repeated the experiment with a solution of
" lead, and also of mercury in the nitrous acid, and
" the result was similar ; horn lead and marine salt of
" mercury were formed "f

In these experiments of Messrs. Monnet and Kir-
wan, 'tis evident that a double affinity takes place in
preference to a single one : for the nitrous acid of
these different nitrates unites with the alkali of the
common salt, while the muriatic acid of the latter
seizes the silver, mercury, and lead, of the nitrates,
and forms muriates of silver, mercury and lead : the
free alkali remaining passive in the mixture.

* M. Monnet Dissolution de Meiaux, p. 159*
tPhil. Tians. Vol. 73. Ah. 1783-

68 fcEDUCTfQKS BY

M. Lavoisier says, " There exists only in nature,
l! as far as we can observe them, cases of double af-
«« finity, often triple, and others perhaps still more
" complicated."!:

Now as water does not promote these reductions
merely by dissolving, and minutely dividing, the par-
ticles of the metallic salts, and condensing the hydro-
gen gas ; and since a double affinity takes place in
preference to a single affinity ; it is obvious that the
water must be decomposed in these reductions in the
following manner.

The hydrogen of the gas unites to the oxygen of
the water, while the hydrogen of the latter unites in
its nascent state to the oxygen of the metal, reduces
it, and forms water.

Thus what could never be effected by a single, is
readily performed by a double affinity.

Hence it follows, that the hydrogen of the gas is
oxygenated by the oxygen of the water, while the
metal is, at the same time, restored to its combusti-
ble state. It also follows, that the quantity of water
formed is double that decomposed.

X Essay on Phlogiston, a new Edit, by xM. Kirwan, p. 46

PHOSPHORUS.

69

CHAPTER II.

REDUCTION OF METALS

BY

PHOSPHORUS,

THE next substance, of whose effects in redu-
cing metals in the fibres of silk, I shall treat, is phos-
phorus, one of the most inflammable substances wc
are acquainted with.

I was for some time at a loss, how to apply it to this
purpose ; but learning from a note of Mr. Lewis,
that it is soluble in ether, I dissolved a small quantity
of it in that fluid, which can be easily effected, if the
ether be, good. The solution is considerably promo-

SO REDUCTIONS BY

ted by a gentle heat, as that of the hand, and may be
made in a small phial, which should be nearly filled
with the ether, and accurately corked ; a common
cork is preferable for this purpose, to a glass stopper ;
and a single -grain of phosphorus is sufficient for a
great number of experiments.

I sometimes applied a much greater degree of heat
than the above, by placing the phial in hot sand,
pressing on the cork at the same time with my fin-
ger, to prevent its being forced out by the expansion
of the ether, part of which is converted into ai
tic fluid, and holds some phosphorus in solution: the
ether soon begins to boil ; the phosphorus melts, and
a strong solution is obtained in a few minutes by
shaking the phial. If the solution be removed to a'
cool place, it frequently deposits crystals.

This manner of preparing the solution is attended
with some danger, for should the phial burst or the
cork be extruded, the contents will be thrown out
with considerable force, and that part of the phos-
phorus not dissolved by the ether burn with great
violence.

The only objection to this preparation of phospho-
rus is the ether, which must necessarily modify the
result, and prevent that simplicity so desirable in ex-
periment.

phosphorus. 71

But, after some observation, it was perceived, that
the ether flies off* and leaves the phosphorus pure,
and minutely divided in the fibres of the silk; the
ether, from its great volatility, first evaporates, and
at the same time, produces a very considerable degree
of cold, which effectually prevents the evaporation,
and combustion, of the phosphorus.

After the ether evaporates, the cold ceases, and the
combustion of the phosphorus commences, attended
with white fumes, which continue till the whole is
consumed, if no other power intervene.

Hence it is evident, that this preparation of phos-
phorus has a simplicity and elegance not always to be
obtained.

It has also another great advantage in experiments
of this kind ; for it does not change in the smallest
degree, the white colour of silk, during its slow
combustion, which is not attended with heat suffici-
ent to affect the most delicate colour. This proper-
ty of not affecting the colour of the silk renders ob-
servation and experiment more accurate ; as what-
ever change supervenes, must depend either on the
metallic solution itself, or on the action of the phos-
phorus on the same. But this advantage is confined
to a certain range of the thermometer •, for if the
heat be increased to about 86° of Fahrenheit, and
the silk be dry, the phosphorus is apt to set fire to it.

72 REDUCTIONS BY

EXPERIMENT I.

GOLD.

I immersed a bit of silk in a solution of gold in
ether, and after the ether evaporated, dropped on it
some of the solution of phosphorus, which diffused
itself through the silk like a drop of oil, and formed
a circumscribed spot, whose limits, as the ether eva-
porated, assumed a brown colour, which soon diffu-
sed itself equally over every part to which the solu-
tion of phosphorus was applied ; but the parts of the
silk, to which the latter did not reach, retained the
yellow colour, which the solution of gold gave them.

The silk viewed by transmitted light presented the
same colours, except that the limits of the brown
appeared more intense, and seemed to border on a
faint purple.

Examining the silk next day, I found that the
whole of the brown stain acquired a faint shade of
purple, which was most evident on the margins of
the stain.

PHOSPHORUS. ?$

EXPERIMENT II.

GOLD.

I dipped a bit of silk in the solution of gold in
ether, and after it was well dried, half of it was wet-
ted with distilled water ; the other half remaining
dry : the solution of phosphorus was applied to both
the moist and dry parts of the silk -, instantly the
part wetted with the water began to acquire a purple
colour ; and soon after the metallic splendour of the
gold appeared ; but that part which was kept dry ac-
quired only a brown stain, similar to that described
in the preceding experiment.

I repeated these experiments many times, and al-
ways found, that the gold was reduced only in pro-
portion to the water applied.

Finding water promoted the reduction of gold by
phosphorus, I began to form various conjectures about
its mode of action ; I first supposed it acted by hold-
ing the particles of the salt minutely divided, thus
diminishing their attraction of cohesion, and conse-
quently increasing their chymical attraction.

The truth of this supposition might, I thought, be
decided by using ether and alcohol, instead of water,
G

74 REDUCTIONS BY

to wet the silk, avoiding aqueous moisture, as much
as possible; accordingly I made the following expe-
riments, which were frequently repeated with nearly
the same result.

EXPERIMENT III.

GOLD.

A piece of silk was immersed in the solution of
phosphorus ; as soon as the ether evaporated, and the
phosphorus began to fume, an ethereal solution of
gold wns dropped on the silk, which immediately got
a brown colour ; the piece was kept constantly wet
with ether, in some time a purple tinge appeared on
parts of the silk, and shortly after small films of re-
duced gold appeared ; the silk was now remarkably
wet, and seemed to have a great power of collecting
water ; this I supposed was partly attracted from the
air by the salt, and phosphorous acid formed during
the combustion, which has a powerful attraction for
water, and partly deposited in the silk by the ether
during its evaporation.

In order to determine if the ether during its eva-
poration deposited water in the silk, I kept a bit of
silk wet with ether for a few minutes, and found,
that after the evaporation ceased, the silk was moist;
but this humidity was not so great, as that observed

PHOSPHORUS. 10

in the silk, to which the ethereal solutions of phos-
phorus and gold were applied.

Another bit of silk was dipped in the ethereal so-
lution of gold, and after the ether evaporated, the
solution of phosphorus was applied ; a brown colour
was produced ; the silk was kept wet with ether, and
in a short time, a purple tinge appeared on parts of
it ; but chiefly at the margin of the stain, which gra-
dually diffused itself over the whole.

The only difference between this and the prece-
ding experiment on gold is the order, in which the
solution of gold and phosphorus -were applied to the
silk, but there is a considerable difference in the re-
sult, for in this the brown and purple colours were
formed much more slowly, and no particles of redu-
ced gold appeared till after a much longer time.

EXPERIMENT IV.

GOLD.

A piece of silk was immersed in the solution of
phosphorus, and when the white fumes began to rise,
a solution of gold in alcohol was applied to the silk,
which was, kept wet with alcohol, a brown tinge
which soon changed to a purple, appeared on diffe-
rent parts, and in a little time after, a very small film
of reduced gold was visible on a part of the margin*.

*"6 REDUCTIONS BY

In another experiment, conducted in the same
manner, the reduction was more evident.

The solution of gold used in this experiment was
very rich, and had a great attraction for water, for
bits of silk tinged with it, could not be dried with-
out difficulty, and after they were removed to a cool
place, they very soon became moist again. This is
more or less the case with solutions of gold in gene-
ral.

EXPERIMENT V.

GOLD.

A bit of silk was dipped in a solution of gold is
alcohol and dried, then some of the solution of phos-
phorus was poured on the silk, a brown and then a
purple colour appeared, and in some parts a small
portion of the gold was reduced, the reduction was
very obscure, but became gradually more evident, in
proportion as it attracted water from the air. The
silk was occasionally wetted with alcohol.

This experiment was repeated, with this difference,
that the silk was not kept wet with alcohol, and no
reduced gold could be perceived.

?H05t»H0L'R'-i.

EXPERIMENT VI.

GOLD.

In order to exclude water more effectually, a small
phial was carefully dried by placing it in hot sand,
and then corked, to prevent the access of moisture
from the air ; when the phial cooled, it was nearly
filled with ether, and a small bit of phosphorus drop-
ped into it, it was then corked and replaced on the
hot sand, the phosphorus soon melted, and a strong
solution was obtained by shaking the phial.

Into this solution a small bit of silk, which was
dipped in a rich solution of gold, and carefully dried,
"was introduced ; the silk immediately got a brown
tinge, but not a particle of reduced gold could be
perceived The solution in a short time became tur-
bid, and deposited a brown powder. The colour of
the precipitate was exactly the same, as that which
the silk acquired. The experiment was continued
about three months, and carefully observed, but no
other change could be perceived ; at the end of this-
time the silk was taken out of the phial, and the so-
lution of phosphorus was found capable of reducing
gold and silver by the aid of water,

G2

78 REDUCTIONS BY

EXPERIMENT VII.

GOLD.

In order to contrast the effects of water with
those of ether, and alcohol, more fully, a piece of
silk was immersed in a solution of nitro-muriate of
gold in water, and dried in the air about twelve
hours ; during which time the yellow tinge, the solu-
tion of gold gave the silk, remained unchanged : the
solution of phosphorus was then applied ; a brown
stain appeared j the ether soon evaporated ; the phos-
phorus began to fume ; and the silk acquired a pur-
ple colour ; but not a particle of reduced gold could
be perceived. The purple tinge in this bit of silk
was much more intense, and more equal, than in the.
pieces, in which ether and alcohol were used.

EXPERIMENT VIII.

GOLD.

I dipped a piece of silk in the solution of phos-
phorus, when the ether evaporated, and the phos-
phorus began to fume, a solution of gold in water
was applied ; instantly the silk was covered with a
splendid coat of reduced gold.

PHOSPHORUS. 7

Nothing can be more striking than this experi-
ment, which was repeated times without number, or
demonstrates the necessity of water in these reduc-
tions in a more convincing manner.

This piece, viewed by transmitted light, had a pur-
ple colour with a considerable tinge of blue ; and the
margin of the reduced gold was fringed with
purple.

EXPERIMENT IX.

GOLD.

Thinking the phosphorus applied in the form of
vapour through the medium of water might be more
effectual than a solution of it in ether, I immersed a
small bit of silk in an aqueous solution of gold, and
suffered it to dry a little ; it was then suspended in a
phial over a little water, into which a small bit of
phosphorus was previously introduced: the phial was
then corked, and placed on hot sand : the phosphorus
began to melt, and ascend in white vapours, which, as
soon as they reached the lower end of the silk, gave
it a brown tinge, succeeded by a purple ; and the
gold began to assume its metallic splendour : in a
short time these appearances were evident over the
whole silk.

80

REDUCTIONS BY

The following propositions are deducible from
these experiments.

1. Water does not promote the reduction of gold
merely by dissolving, and minutely dividing, the
particles of the salt, and thus diminishing their at-
traction of cohesion, and consequently increasing
their chymical attraction, as I first supposed ; for
were this the case, ether and alcohol, which equally
dissolve and divide the salt, should produce the same
effect.

2. Ether and alcohol do not promote these reduc-
tions without the aid of water ; for it is evident from
the experiments related, that the few particles of re-
duced gold which appear when they are employed,
depend entirely on the quantity of water which they
leave in the silk during their evaporation, and that
attracted from the air by the solution of gold, and by
the phosphorus during its combustion, both of which
have a strong attraction for water.

3. Phosphorus does not reduce gold by giving the
metallic earth phlogiston, as the Phlogistians suppose;
for were this opinion true, a solution of gold ia
ether, or alcohol, should be reduced by the phospho-
rus as effectually as a solution of gold in water is.

4. Phosphorus does not reduce gold, by combining
with, and separating, the oxygen of the gold, as the

PHOSPHORUS. 8 1

Antiphlogistians assert ; for were this the case, the
particles of the phosphorus so attenuated by the
ether, should reduce a solution of gold in ether, or
alcohol, as well as a solution of gold in water, since
the impediment opposed by the attraction of cohesion
is equally removed in both cases.

I shall conclude these remarks on the reduction of
gold with the following experiment, which often
amused me.

EXPERIMENT X.

GOLD.

A small bit of silk was immersed in a solution of
gold in ether, and dried * then the solution of phos-
phorus was applied, which changed the yellow colour
of the silk to a brown : when the phosphorus began
to fume, I placed the silk on the palm of my hand,
and breathed on it a considerable time ; a purple
tinge gradually succeeded the brown, and in some
little time after, the metallic lustre of the gold began
to appear.

The same experiment succeeds with a solution of
gold in alcohol.

82 REDUCTIONS BY

Another bit of silk, treated in the same manner,
was placed over the vapour of warm water for some
time ; the same appearances took place, and particles
of reduced gold were evident in the silk.

If the water, whence the vapour arises, be too
hot, the heat retards, and sometimes prevents, the
reduction, by volatilizing the phosphorus.

EXPERIMENT XI.

SILVER.

I dipped a bit of silk in a solution of fused nitrate
©f silver in alcohol, and dried it in the air : then
some of the solution of phosphorus was applied,
which produced a brown stain, whose margin, after a
few minutes exposure to the air, acquired a livid
white appearance, caused by a partial and imperfect
reduction of the silver.

This, however, would not be taken by a person
unacquainted with experiments of this kind for re-
duced silver.

PHOSPHORUS. «>•*

EXPERIMENT XII.

SILVER.

A bit of silk was immersed in the solution of phos-
phorus ; as soon as the ether evaporated, and the
phosphorus began to fume ; a few drops of the solu-
tion of silver in alcohol were applied : immediately a
black stain, intermixed with some brown, appeared;
and, after some time, obscure films of reduced silver
presented themselves i these appeared on different
parts of the stain, but were so minute as to be scarcely
visible. The only difference between this and the
preceding experiment is the order, in which the so-
lutions were applied ; but even this modifies the re-
sult in some measure.

That these imperfect reductions depended on wa-
ter, deposited in the silk by the alcohol, during its
evaporation, or attracted from the air by the phos-
phorus during its combustion, will appear from the
following experiment.

EXPERIMENT XIII.

SILVER.

A small phial was well dried in hot sand, then
corked, and removed to a cool place : after the phial

84> REDUCTIONS BY

cooled, it was nearly filled with ether, and a small
bit of phosphorus which was repeatedly washed in
alcohol to free it from any aqueous moisture, that
might adhere to it, was introduced ; the phial was
then corked and placed in hot sand; when the phos-
phorus melted, I shook the phial and obtained a
strong solution.

Into this solution a small bit of silk, which was
dipped in a solution of silver in alcohol, and dried,
was introduced; the phial was corked, the silk in-
stantly assumed a brown colour, but not a particle of
reduced silver could be seen, though the experiment
was continued about three months, nor did the solu-
tion of phosphorus become turbid, or deposit any
precipitate, as happened in similar experiments on
gold.

At the end of this period the silk was taken out
of the phial wetted with water, and suspended in a
window, and after a considerable time, reduced sil-
ver was manifest on different parts of the silk.

"With the solution of phosphorus, in which the
silk stood during that time, I reduced gold and silver
with the assistance of water.

In order to compare the effects of water with those
of ether and alcohol, I made the following experi-
ments.

Phosphorus. 85

experiment xiv.
SILVER.

I dipped a bit of silk in a solution of nitrate of
silver in water, and dried it at the fire ; the silk thus
dried retained its white colour, the solution of phos-
phorus was then applied, and immediately produced
a brown colour, which soon, in proportion as the
phosphorus fumed acquired a deeper tinge verging on.
black, and slight signs of reduction appeared after a
little time on the margin of the stain.

Another bit of silk, treated in the same manner,
but dried much better, exhibited still fainter signs of
reduction, for the brown stain did not appear on this:'
piece as soon as on the former, nor was it so intense;
however, after some minutes exposure to the air, the
stain became deeper, and its margin acquired a livid,
white appearance, owing to a partial reduction of the
silver.

It has been often remarked, that the reduction
commences first on the margin of the stain, which
the solution of phosphorus and that of the metal
produce in the silk ; I was a long time at a ioss to ac-
count for this appearance, but the cause was acci-
H

£$ REDUCTIONS BY

dentally discovered; for happening to spill a few drops
of the solution of phosphorus on a table, I observed,
that as they evaporated, watery circles were formed
round the spaces on which the drops fell, and that
all the parts within the circles were dry.

This explains why the reduction begins on the
margin of the stain.

I observed the same of alcohol, for if it be drop-
ped on a level surface, it leaves a watery ring behind,
though not near so soon as a solution of phosphorus
in ether does ; this is the reason why alcohol seems
to promote the reduction of some metals ; I say seems,
for it does not promote it, but in proportion to the
quantity of water it contains, or attracts from the
air, and deposits in the silk during its evaporation.

How essential water is to the reduction of metals
will appear from the following experiment.

EXPERIMENT XV.

SILVER.

I immersed a piece of silk in the solution of phos-
phorus, and after the ether evaporated, and the phos-
phorus began to fume, a solution of nitrate of silver

PHOSPHORUS. 87

in water was applied ; instantly the silver was resto-
red to its metallic splendour.

This experiment is very amusing, and well calcu-
lated to strike the beholder with surprise.

The reduction is sometimes attended with spangles
of a beautiful blue, which appear chiefly where the
solution of silver is most abundant.

The solution of silver is commodiously applied by
a camel's hair pencil.

I also tried the effects of the vapour of phospho-
rus on bits of silk dipped in a solution of nitrate of
silver in water, and exposed to the vapour, in the same
manner as in experiment the 9th, and the silver was
•lwoys reduced ; but a solution of phosphorus in ether
seems preferable to the vapour.

A small glass tube, resembling a thermometer,
with its bulb terminating in a smaller and nearly ca-
pillary tube, I found useful, and economic, especially
in experiments on gold : by immersing the smaller
end in the metallic solution, and inspiring through the
tube at the same time, the bulb may be filled : by
this means a single drop, or more if necessary, may
be applied to the silk j and thus a great number of
experiments can be made on a single grain, or a much
less quantity of gold, or any other metal.

88 REDUCTIONS BY

This little instrument may be used also to app\y
the solution of phosphorus to the silk ; and it
was by using it for this purpose, I discovered, that
phosphorus has not the power of reducing silver
without the aid of water •, for blowing the solution
of phosphorus from the tube on bits of silk, which
had been dipped in a solution of silver and dried,
I was surprised to find films of reduced silver fre-
quently appear •, whereas none appeared, when I
applied the solution of phosphorus in a different
manner : this unexpected event often occurred, be-
fore I learned the cause *, at length I suspected it
might depend on the moisture of the breath ; and I
was soon convinced by moistening the silk with wa-
ter, that the suspicion was well founded.

It is evident from these experiments on silver,
that water is essential to the reduction of this metal
by phosphorus ; and that ether and alcohol do not
promote it.

It is also evident that these experiments, and those
made on the reduction of gold, mutually illustrate
each other ; and confirm the conclusions drawn
from them.

PHOSPHORUS. 8$

EXPERIMENT XVI.

PLATINA.

I immersed a bit of silk in a solution of nitro-mu-
riate of platina in distilled water and dried it in the
air; the solution of phosphorus was then applied to
the silk but no appearance of redu&ion could be
perceived.

Another bit of silk was dipped in the solution of
phosphorus ; when the ether evaporated and the
phosphorus began to fume, the solution of platina
was applied to the silk, and in some time, delicate
films of reduced platina were visible where the water
was most abundant. These films of platina com-
monly disappear, and nothing remains but a brown
tinge which, however, is more intense than what the
solution of platina alone gives the silk.

To succeed in this experiment the silk should be
replete with phosphorus, which is easily done by ap-
plying the solution twice or thrice, and waiting after
each application till the fumes begin to appear. It
is also necessary to keep the silk constantly wet with*
wate . Sometimes it requires from ten to twenty
minutes to reduce platina in this manner.

2 H

S ® REDUCTIONS BY

EXPERIMENT XVII.

MERCURY.

I dipped a bit of silk in a solution of oxygenated
muriate of mercury and dried it in the air j then the
solution of phosphorus was applied ; when the ether
evaporated and the phosphorus began to fume, a
yellow stain commenced on the margin and gradual-
ly appeared over the whole.

To compare the effects of different degrees of
moisture, I immersed a bit of silk in the same solu-
tion of mercury, and dried it carefully at the fire ;
the solution of phosphorus was then applied ; the
silk began to fume, but no change except a very
slight ring of a yellow hue appeared. The rest of the
silk retained its white colour.

Another bit of silk was immersed in the solution
of phosphorus ; when the ether evaporated and the
phosphorus began to fnme, the same solution of
mercury in distilled water was applied, and in a few
seconds a bright film of reduced mercury was visible
on the margin of the part to which the metallic solu-
tion was applied, and after some time appeared on
the whole. The reduction was attended with the
colours of the rainbow.

PHOSPHORUS. 91

After a little time these colours vanish and the
metallic film becomes much more obscure, accord-
ing as the silk dries, and is succeeded by a yellow
stain.

EXPERIMENT XVIII.

MERCURY.

A bit of silk was dipped in a solution of nitrate of
mercury in distilled water, and dried at the fire •,
then the solution of phosphorus was applied ; and
when it began to fume, a brown stain commenced at
the margin, which soon diffused itself over the
whole and gradually acquired a faint tinge of black.

Another piece of silk, treated in the same manner,
but dried in the air, exhibited the same appearances ;
except that the brown tinge verged more on black.

Another bit of silk was immersed in the solution
of phosphorus, and when it began to fume, the solu-
tion of nitrate of mercury was applied ; a brown co-
lour instantly appeared, accompanied with a film of
reduced mercury, which was most evident where the
metallic solution was most abundant. This film soon
disappeared and was succeeded by a black stain, in
which, however, reduced mercury was visible. No

92 REDUCTIONS BY

colours but black and brown appeared in this expe-
riment.

It appears from these experiments on mercury,
that the reduction kept pace with the quantity of
water present.

EXPERIMENT XIX.

COPPER.

A piece of silk was immersed in a solution of sul-
phate of copper and dried in the air : then a strong
solution of phosphorus was applied ; the silk acquired
a brown colour, but no other visible alteration oc-
curred.

Another piece of silk was dipped in the same so-
lution of copper and dried at the fire much better
than the preceding ; the solution of phosphorus was
applied ; when the ether evaporated and the phos-
phorus began to fume, a brown tinge commenced on
the margin of the silk, and gradually diffused itself
over the whole ; but the stain was by no means so
intense as that produced in the preceding piece ; so
that there can be no doubt that the difference was
owing to the different degrees of moisture in the
silk.

PHOSPHORUS.

After this piece remained in the air for some
time, the brown tinge became more intense, a proof
that it attracted water from the air. This difference
in rhe appearances of pieces dried in the air and at
the fire, I frequently remarked.

EXPERIMENT XX.

COPPER.

A strong solution of phosphorus was applied to a
piece of silk, when the ether evaporated and the
phosphorus began to furne, a solution of sulphate of
copper was applied ; a brown stain was instantly pro-
duced, and its margins were soon covered with a
white metallic film, parts of which, after some time,
verged en the colour of copper, intermixed with
purple, green and blue. If the solution of phospho-
rus be weak, which is always the case when the
ether is bad, nothing appears on the silk but the
brown stain and the white metallic film. As the
silk dries most of these appearances vanish ; but
some of the blue tinge survives, and the silk looks
very unseemly.

A bit of silk was immersed in the same solution of
copper, and exposed to the vapour of phosphorus, as
in experiment the 9th, but no change was produced
on the silk, except a few brown spots, though the

94 SEDUCTIONS BY

heat was such that the vapour filled the phial, and
circulated through it : the vapour corroded a brass
pin which was used to suspend the silk in the phial.
This induced me to try its effects on copper, which
was corroded by it in a remarkable manner, and
changed into a black substance resembling a mixture
of charcoal and oil. It appears then that phosphorus
i's ill adapted to the reduction of this metal.

EXPERIMENT XXI.

TIN.

A bit of silk was immersed in a solution of mu-
riate of tin in distilled water, and dried in the air,
the solution of phosphorus was then applied to the
silk, and though it fumed considerably, no changi
whatever could be perceived in the colour of the silk,
nor was there the smallest appearance of reduction.

I poured some of the solution of phosphorus on a
bit of silk, and when it began to fume the solution
of tin was applied ; after a few seconds, white metal-
lic films appeared, first on the margin, and were gra-
dually diffused over that part of the silk to which the
muriate of tin was applied, a yellow colur intermix-
ed with red sometimes attends the reduction. After
some little time these films of reduced tin vanish, and
scarcely leave a stain behind.

PHOSPHORUS. 95

I did not succeed in reducing acetite of lead, mu-
riate of arsenic, or sulphates of iron, and zinc, in
this way.

These experiments on tin shew that water is es-
sential to its reduction by phosphorus, 2nd give ad-
ditional force to the preceding conclusions.

M. Sage discovered that gold, silver, &c. are pre-
cipitated from their solutions in the metallic form,
by pieces of phosphorus, which are covered at the
same time with bright coats of gold, silver, &c.

To determine if water were essential to these re-
ductions performed by M. Sage, I made the follow-
ing experiments.

EXPERIMENT XXII,

GOLD.

Some solution of phosphorus in ether was poured
into a china cup, and a few drops of the ethereal
solution of gold were added, instantly a brown pow-
der was precipitated similar to what appeared in ex-
periment the 6th, but no gold in its metallic form
could be perceived.

96 REDUCTIONS BY

EXPERIMENT XXIII.

GOLD.

A solution of nitro- muriate of gold in water was
poured into a china cup, containing a solution of
phosphorus in ether, instantly the gold began to as-
sume its metallic splendour, attended with a variety
of colours, as purple, blue, and red, the beauty of
which cannot be described ; the quantity of the blue
was gradually diminished, and what remained, was
dispersed over the surface in small films, intermixed
with spangles of reduced gold. Most of the blue
films were of a circular figure, some had a central
speck of ruby red, and were fringed with purple;
some had a round eentral speck of a darker blue than
the surrounding parts, and some were of an irregu-
lar figure, fringed with purple or ruby red. I often
observed these blue films assume the real colour of
gold without suffering any intermediate change of
colour, and I think, I observed the same of one of
the largest specks of rifby red, that appeared in this
experiment. All these colours disappeared, when
the reduction was completed.

The variety of colours, which these films assume,
depends on the different degrees of reduction ; that
is to say, on the quantity of oxygen combined with

PHOSPHORUS. 9V

the metal, in proportion as the metal is deprived of
the oxygen, it assumes various colours, which often
succeed each other in a regular order, shewing the
different stages of the reduction ; thus when gold is
reduced, the first perceptible change is a green which
soon becomes olive, this is succeeded by blue and
purple, and sometimes by a ruby red ; the purple
tinge is a mixture of blue and red.

The various colours which metals and their calces
communicate to glass and other substances, are ex-
plicable on these principles, and the difficulty of ob-
taining a ruby-coloured glass by gold is readily under-
stood from the facility with which that metal parts
with oxygen.

EXPERIMENT XXIV.

GOLD.

A thread was passed by means of a needle through
a small bit of phosphorus which was freed from -<ny
moisture that might adhere to it, by immersing it for
some time in alcohol, it was then suspended by means
of the thread in a solution of gold in ether, contain-
ed in a phial, which was carefully dried in hot sand;
in a few minutes the solution became turbid, an ef-
fervescence commenced, and a brown precipitate was
I

SO REDUCTIONS BY

formed ; according as the precipitate fell the solution
became clear, lost its yellow colour, and the whole
of the gold seemed to have been precipitated, but
not a particle of reduced gold could be seen.

Another bit of phosphorus was suspended in the
same manner in a solution of nitro-muriate of gold
in water, and in a few minutes got a splendid coat of
reduced gold.

EXPERIMENT XX'

SILVER.

A few drops of a solution of fused nitrate of silver
in alcohol were poured into a china cup containing a
solution of phosphorus in ether j instantly a black
precipitate with a tinge of brown was formed, but
no silver in its metallic state could be perceived.

After some time the precipitate attracted moisture
from the air, and some films of reduced silver ap-
peared.

The same experiment was made in a phial, which
orked to exclude the moisture of the air, and
nothing but the black precipitate appeared.

PHOSPHORUS.

99

Some of the same solution of silver was diluted
■with water, and dropped on a solution of phosphorus
in ether, and instantly films of reduced silver floated
on the surface.

EXPERIMENT XXVI.

SILVER.

A bit of phosphorus was suspended by a thread in
some of the same solution of silver in alcohol, con-
tained in a phial carefully dried, a black precipitate
with a tinge of brown soon appeared, but no silver
in its metallic state could be observed; part of the
precipitate adhered to the phosphorus, and part fell
to the bottom of the phial.

- In another experiment made in a phial not suffici-
ently dried, a few small films of reduced silver were
observed on the sides of the phial, but not a pprticle
of silver in its metallic form could be seen on the
phosphorus.

Another bit of phosphorus was suspended in a di-
luted solution of nitrate of silver in water, and in
some hours, the phosphorus was covered with redu-
ced silver.

100 REDUCTIONS BV

The case of silver, which covered the phosphorus
prevented its spontaneous combustion in the air ; the
same was observed of the bit of phosphorus coated
with gold.

Hence it appears, that M. Sage's success in redu-
cing metals by phosphorus, depended on the water of
the metallic solution.

These experiments were often repeated with near-
ly the same result, but some variety often occurs,
depending on various circumstances, as the strength
of the metallic solution, and that of the phosphorus,
the quantity of water present, and the purity of the
materials employed.

It is difficult to obtain ether, or alcohol, with the
least possible quantity of water, and equally difficult
to expel all moisture from the surface of glass ; for
this reason the bits of phosphorus in the experiments
made with alcohol and ether, were suspended by
threads, so as not to touch the sides of the glass.

I shall conclude this chapter with a general view
of the inferences, which seem naturally to flow from
these experiments with phosphorus.

1. Water is essential to the reduction of metals by
phosphorus, for these experiments shew that the re-

PHOSPHORUS. 101

duction is effected only in proportion to the quantity
of water present.

2. Phosphorus does not reduce the metals by gi-
ving them phlogiston.

3. Phosphorus does not reduce the metals by uni-
ting with, and separating their oxygen.

How then is the reduction effected ? are we not
to conclude, that it is effected by the decomposition
of the water, in the following manner ?

The phosphorus attracts the oxygen of the water,
while the hydrogen of the atter unites in its nascent
state with the oxygen of the metal, and effects the
reduction.

Hence it follows, that the phosphorus is oxygena-
ted by the oxygen of the water, while the metal is
restored to its combustible state.

Thus what could never be affected by a single, is
readily performed by a double affinity, which always
takes place in preference to a single affinity, as the
experiments of Messrs. Monnet and Kirwan, men-
tioned in the preceding chapter, shew.
12

102 REDUCTIONS BY

It is well known, that phosphorus kept in water
acquires an oxygenated crust, which could not hap-
pen without a decomposition of the water ; this fact
serves to confirm the explanation here offered.

And indeed the decomposition of water in these
experiments must be granted, or it must be supposed,
that water itself reduces the metals by uniting with
their earths, and constituting their phlogiston ; or by
uniting with, and separating their oxygen •, supposi-
tions repugnant to our present knowledge of chy-
mistry.

SULPHUR. 103

CHAPTER III.

REDUCTION OF METALS

BY

SULPHUR.

THOUGH Sulphur, as far as my reading extends,
has seldom been considered as a reducer of the me-
tals, yet as it holds a distinguished rank among com-
bustible bodies, analogy led me to examine its powers
in reducing and fixing the metals in the fibres of
silk.

The vapour of sulphur appeared to be the most
simple form in which it could be applied to this pujc-

104) REDUCTIONS BY"

pose, and may be obtained by placing a phial con-
taining flowers of sulphur in hot sand •, as the sulphur
melts, it assumes the form of vapour, which soon
fills the phial, expels the atmospheric air, and bears
a considerable heat before it inflames; a bit of silk
prepared for the experiment may be held over the
vapour as it issues from the phial, or immersed in it.
The neck of the phial should be of a convenient size
for this purpose.

But these experiments are more conveniently made
by means of a sulphurous match, and a glass funnel,
in which the silk imbued with the metallic solution
may be suspended by a thread passed through it, and
made fast with a cork, which also serves to confine
the vapour.

The glass is then placed on a table, and by moving
it a little beyond the verge of the same, a lighted
match is readily introduced, which, as soon as the
glass is filled with vap ur, may be withdrawn ; the
vapour is confined by making the glass glide back on
the table ; and thus the phenomena of the experi-
ment can be easily observed.

Though the vapour obtained in this manner be
chiefly sulphurous acid gas ; yet its effects are not
less interesting on that account.

SULPHUR. 10 ^

EXPERIMENT L.

GOLD.

A bit of silk was dipped in a solution of gold in
ether and dried, it was then suspended in the glass
funnel, and exposed for some time to the vapour ob-
tained from a burning match •, but no change could
be perceived, except that the silk became a little
brown.

Another bit of silk prepared in the same manner
was immersed in the vapour of sulphur, formed in a
phial placed in hot sand, with the same result.

EXPERIMENT II.

GOLD.

A piece of silk was immersed in a solution of ni-
tro muriate of gold in water, suspended in the glass
funnel, and exposed while wet to vapour of sulphur,
formed by a burning match ; no sooner did the va-
pour touch the silk than the reduction commenced,
and in a few seconds the whole piece was covered
with a splendid coat of reduced gold, permanent and

108 REDUCTIONS BY

retentive of its lustre, but had a few specks of a dull
violet hue.

The silk viewed by transmitted light appeared of
a beautiful blue colour ; and being removed from the
vapour, and suspended in the air, began in about ten
minutes to exhale a vapour which continued about
two hours, and smelled acid and pungent.

Another bit of silk, dipped in the same solution of
gold and dried, was wetted with alcohol and exposed
to the same vapour : the silk acquired a brownish
hue, and a small white metallic film appeared on its
lower end, where the alcohol most abounded : the
silk was then wetted with water and replaced i»
the vapour ; instantly a lively purple with a bright
pellicle of reduced gold appeared.

EXPERIMENT III.

SILVER.

A piece of silk was immersed in a solution of ni-
trate of silver in water, and suspended in the air of a
dark closet to dry; the silk retained its white co-
lour, though it remained in the air twenty. four
hours; it was then exposed fourteen hours to the
vapour obtained from a burning match ; but suffered

suLrHUR. 107

no change, except that it acquired a brown tinge :
it was now wetted with alcohol, and replaced in the
vapour for sometime; no signs of reduction appear-
ing, it was wetted again with the alcohol and expo-
sed to the vapour : but still no signs of reduction
could be perceived : I then wetted the silk with dis-
tilled water, replaced it in the sulphureous vapour ;
and in about a minute reduced silver appeared.

EXPERIMENT IV.

SILVER.

I dipped a bit of silk in a solution of nitrate of sil-
ver in distilled water, and exposed it, while wet, to
the vapour of sulphur, as in the preceding experi-
ment ; in a few seconds the silver appeared in its
metallic form, attended with a variety of lively co-
lours : the most remarkable of these were a pleasant
blue, orange, purple and yellow, which soon disap-
peared : the reduced silver rlso disappeared in a
great measure, some faint traces only remaining.
The silk was removed from the vapour into the air,
but exhated no vapour, as happened in experiment
the second.

A small bit of sulphur was suspended in a phial
containing a solution of nitrate of silver in water ; and

108 REDUCTIONS BY

after some weeks the sulphur was coated with redu-
ced silver of no great lustre.

EXPERIMENT V.

PLATINA.

A bit of silk was immersed in a solution of nitro-
muriate of the ore of platina in distilled water, and
dried in the air; it was then suspended in the glass
funnel, and exposed to the vapour of a burning
match : but no signs of reduction could be observed ;
the silk retained the colour the solution gave it.

Another bit of silk was dipped in the same solu-
tion of platina, and exposed, while wet, to the sul-
phureous vapour ; in a few seconds the reduction
was very evident. The silk was immerged in a glass
of clear water, and transferred bright films of redu-
ced platina to the surface of that fluid ; most of them
were of the same colour as the spangles in the ore of
platina; and some were distinguished by lively blue
and purple colours.

Another bit of silk, dipped in the same solution of
platina, was immersed, while wet, in the vapour of
sulphur, formed in a phial placed in hot sand ; the
reduction soon commenced, and was much more per-

SULPHUR. 109

fe& and permanent than in pieces exposed to the
vapour obtained from ignited matches.

It is remarkable that sulphur reduced this metal
much better than phosphorus or hydrogen gas did,
but the reduced platina disappears after some time,
and leaves nothing behind but a brown stain.

If the films be transferred from the silk to water,
they may be preserved in their metallic form.

EXPERIMENT VI.

MERCURY.

A bit of silk was immersed in a solution of nitrate
ef mercuiy in distilled water, and dried; parts of the
siik immediately acquired a slate colour; the silk was
then exposed to the vapuur of sulphur, obtained from
a burning match, but it suffered no change, except
that the colour became a little more intense.

Another bit of silk was dipped in the 'same solu-
tion of mercury, and exposed while wet to the same
vapour ; the reduction instantly commenced tri a very
evident manner, accompanied with several colours,
as blue, purple and yellow.

K

110 REDUCTIONS BY

The silk was removed from the vapour and soon
lost most of its lustre, which was succeeded by a
slate colour, through which some particles of reduced
mercury were observed to shine.

EXPERIMENT VII.

MERCURY.

A bit of silk was immersed in a solution of oxyge-
nated muriate of mercury in water and dried in the
air ; it was then exposed to the sulphureous vapour
obtained from a burning match ; but the silk under-
went no visible change. This solution of mercury
does not change the white colour of silk, as that of
nitrate does.

Another bit of silk was dipped in the same solution
of oxygenated muriate of mercury, and exposed,
while wet, to the vapour ; in a few seconds reduced
mercury appeared, unattended by any colour, except
a slight tinge of citron yellow on part of the silk.
After some time the whole of the reduced mercury
vanished.

SULPHUR. HI

EXPERIMENT VIII.

COPPER.

A piece of silk was immersed in a solution of sul-
phate of copper and dried ; It was then suspended in
the glass funnel and exposed to the vapour obtained
from a burning match ; but the silk suffered no
change, retaining the colour, which the solution
gave it.

Another bit of silk was dipped in the same solution
of copper and exposed, while wet, to the vapour of
an ignited match ; in a short time a white metallic
film appeared, accompanied with a brown tinge :
the silk becoming dry was wetted with water and ex-
posed to a brisk vapour from another match -, the
film became more evident and parts of it verged on
yellow, bordering on a copper colour. After some
time this white metallic film disappears, and nothing
remains but a light brown stain.

EXPERIMENT IX.

LEAD.

A bit of silk was immersed in a solution of ace-
tite of lead in distilled water, and dried in the air ; it

112 REDUCTIONS BY

was then exposed to the sulphureous vapour of .a
burning match ; but underwent no visible change
whatever.

Another bit of silk was clipped in the same solution
of lead, and exposed, while wet, to the vapour; re-
duced lead soon appeared all over the silk ; but after
5 rime this reduced lead disappears, unless it be
transferred to the surface of water.

EXPERIMENT X.

TIN.

A bit of silk was immers?d in a solution of muri-
tin m distilled water, and dried in the air : it
was then exposed to the vapour obtained from a
burning match, which soon filled the glass ; but pro-
duced no visible change on the silk.

Another bit of silk was dipped in the same solu-
tion of tin, and exposed, while wet, to the sulphure-
ous vapour ; and in a few seconds reduced tin ap-
peared all over the silk ; but the tin soon disappears,
if net transferred to water.

SULPHUK- 113.

EXPERIMENT XL

ARSENIC.

A bit of silk was immersed in a solution of muriate
of arsenic in distilled water, and dried in the air ; it
was then exposed to the vapour of sulphur, obtained
from a burning match ; but the silk suffered no ap-
parent alteration.

Another bit of silk was dipped in the same solution
of arsenic, and exposed, while wet, to the vapour :
in a few seconds the arsenic was reduced, but not in
a very evident manner ; the silk was immerged in
water, and several bright films of reduced arsenic
floated on the surface of that fluid.

EXPERIMENT XII.

BISMUTH.

A bit of silk was immersed in a solution of nitrate
of v.h in distilled water, and dried in the air ;

it was then exposed to the vapour of sulphur obtained
K2

i 14> UCTIOKS BY

from a burning match , but no signs of reduction ap-
pealed.

Another bit of silk was dipped in the same

□ of bismuth, and exposed, while wet, to the

apour j the bismuth was soon reduced,

with a brown stain j but the metallic

l&stre sjOi. .red.

EXPERIMENT Kill.

ANTIMONY.

A piece of silk was immersed in a solution of tar-
trite of antimony in water, and dried ; it was then
exposed to the vapour of a burning match; but no
ge could be observed ; nor did the silk immer-
ged in water deposit any films on its surface.

Another piece of silk was dipped in the same solu-
tion of antimony, and exposed, while wet, to the va-
pour : the silk, in a few seconds, acquired a yellow
colour, and a bright bluish film of reduced antimony
appeared on the lower end of the silk, where the
water was most abundant: the silk was then immer-
ged in a glass of water, and transferred a large pelli-
cle of reduced antimony to the surface of that fluid.

SULPHUR. 11.5

EXPERIMENT XIV

IRON.

A bit of silk was immersed in a largely diluted so-
lution ot sulphate of iron in distilled water, and dried
in the air, it was then exposed to the vapour of sul-
phur obtained from a burning match ; after some
time the colour of the silk became a little brown, but
no reduced iron 'could be seen, nor did the silk im-
merged in a glass of clear water transfer any thing
metallic to its surface.

Another bit of silk was dipped in the same solu-
tion of iron, and exposed while wet to the sulphure-
ous vapour •, in a short time the sii!' was withdrawn,
and a minute shining film of a livid white colour,
was visible on its lower margin, where the water most
abounded •, the silk was then immerged in a glass of
water, and transferred a large film of reduced iron
to its surface.

This experiment succeeded also with the vapour of
sulphur formed in a phial placed on hot sand. The
fil is of reduced iron were seldom visible on the silk,
bin were soon rendered visible by transferring them
to water.

116 REDUCTIONS BY

EXPERIMENT XV.

ZINC.

A piece of siik was dipped in a diluted solution of
sulphate of zinc and dried, it was then exposed to
the vapour obtained from a burning match, no change
whatever could be perceived ; the silk was immerged
in a glass of water, but deposited no film on its sur-
face.

Another piece of silk was dipped in the same so-
lution of zinc, and immersed while wet in the va-
pour of sulphur formed in a phial placed on hot sand;
in about half a minute the siik was withdrawn from
the vapour, and some parts of it had a shining livid
appearance, which I took for reduced zinc; in order
to determine if the reduction were real, the silk was
immerged in a glass of clear water, and transferred
to its surface a bright film of reduced zinc.

If the silk be kept too long in the vapour, some
sulphur will be condensed on its surface, and give it
a yellow colour ; if it be then dipped in a glass of
warer, it will deposit both the sulphur and the me-
tallic films on its surface, but the appearance of the
sulphur is so different from that of the reduced me-
tal, that they are easily distinguished,

LPHUR. 117

Another bit of silk was immersed in a largely di-
luted solution of muriate of zinc, and exposed while
wet, to the vapour obtained from a burning match ;
the silk being withdrawn exhibited -a few minute shi-
ning films on its lower end, and on immersion in wa-
ter left bright films of reduced zinc floating on the
surface of that fluid.

Very often these films cannot be seen, until they
are transferred to water, which I found a very useful
test in doubtful cases ; they are better seen in the
gray light than in sunshine.

These experiments on the reduction of metals by
julpimr wcic often repeated with nearly the same re-
sult •, but some variety occurs depending on the quajn-
ti , of water present, the strength of the metallic
solution, and sulphureous vapour, and also on the
time the silk, is exposed to the vapour.

When the experiments are made in a phial placed
in hot sand, part of the metallic solution frequently

ps from the silk, and falling on the bottom, or
sides of the phial is reduced, covering these parts
with a metallic crust, on which the sulphur soon re-

, and changes the greater part into a sulphure.
The phial commonly cracks.

The following conclusions are deducible from the
experiments related in this chapter.

118 REDUCTIONS BY

1. Water is essential to the reduction of metals by
sulphur, for this effeft is always in proportion to the
quantity of water present.

2. Alcohol does not promote these reductions with-
out the aid of water.

3. Sulphur does not reduce the metals by giving
them phlogiston, nor by uniting with and separating
their oxygen, for were either of these opinions just,
the sulphur so minutely divided by heat, should re-
duce metallic solutions in alcohol as effectually as it
does metallic solutions in water.

When we compare these reductions by sulphur,
with those effected by phosphorus, and consider that;
water is essential to both, we must conclude, that the
reduction is effected in the same manner, viz. by the
decomposition of water, which may be thus explain-
ed.

The sulphur attracts the oxygen of the water,
while the hydrogen of the latter unites in its nascent
state to the oxygen of the metal, and restores it to

the metallic form.

Hence it follows, that the sulphur is oxygennted
by the oxygen of the water, while the metal is re-
stored to its combustible state.

SULPHUR. J 19

It also follows, that a quantity of water equal to
that consumed is formed by the hydrogen of the wa-
ter, and the oxygen of the metal.

This explanation is supported by a fine experiment
of Dr. Priestley, who obtained inflammable air by
passing the vapour of water through sulphur heated
in an earthen tube;* and farther confirmed by the
experience of some judicious makers of oil of vitriol,
who always sprinkle the sulphur with a certain pro-
portion of water, before they inflame it.

The decomposition of water in these reductions
must be granted, or it must be supposed that a single
takes place in preference to a double affinity; which
cannot be admitted.

These experiments point out several errors in M.
Lavoisier's Table of the Affinities of the Oxygenous
Principle ; for he has placed sulphur at a much great-
er distance from that principle than any of the me-
tals treated of in this chapter except gold, and even
in this instance his table is erroneous, unless it be
proved that sulphur reduces metals by directly uni-
ting with, and separating their oxygen ; a supposi-
tion which implies, that the reduction is effected by a
single affinity, and therefore inadmissible.

• Priestley, Vol. VI. p. 150.

12© REDUCTIONS BY

I shall close this chapter with a short extra& from
the Chymical Essays of Bishop Watson, as it seems
to have some relation to the experiments related
here.

His lordship says, that his experiments on " the
" Derbyshire lead ore instruct us to believe, that the
« lead in this kind of ore is in its metallic state; as
tl the ore was changed into lead without the addition
" of any substance containing the inflammable prin-
« ciple."*

But the reduction of lead by sulphur and water,
related in this chapter, points out an evident source
of the inflammable principle ; for the ore itself must
contain some water, a constituent part of which is
hydrogen, or the base of inflammable air; beside his
•lordship thinks no appearance of lead would have ta-
ken place, had there been no communication with
the external air ; but as air always holds water in so-
lution, an ample source of the inflammable principle
is evident.

Cnem. Essaye, Vol. III. p. 219.

ALKALINE SULPHURE. 121

CHAPTER IV.

REDUCTION OF METALS

BY

ALKALINE SULPHURE,

THE Sulphure I made use of, was prepared by
fusing equal parts of carbonate of potash and flowers
of sulphur, till the effervescence ceased.

M. Gengembre has made a very important ob-
servation on alkaline sulphure, prepared in this
way, which is, that this substance has no smell, and
that it exhales no gas while it continues dry, but that
v;hen it is dissolved in water, or attracts humidity
from the air, it diffuses an offensive smell.
L

122 REDUCTIONS BY

From this circumstance M. Gengembre inferred,
that the disengagement of this gas depended on the
decomposition of water ; for he discovered both by
analysis and synthesis, that this air consists of hydro-
gen, one of the principles of water, combined with
sulphur and caloric.

There can then be no doubt, but alkaline sulphure
has the power of decomposing water ; and may there-
fore be happily employed to illustrate the mode of
adtion of sulphur, and other combustible substances,
treated of in this essay.

When diluted acids are poured on solid alkaline sul-
phure, the decomposition of the water is promoted
and accelerated, sulphurated hydrogen gas being
formed in great abundance.

I made two solutions of this alkaline sulphure,
one in water, and the other in alcohol.

EXPERIMENT I.

GOLD.

A bit of silk was immersed in the solution of sul-
phure in alcohol, and then a solution of gold in ether
Was applied •, a brown matter was formed in the silk,
but no reduced gold could be perceived.

ALKALINE SULPHURE. 123

Another bit of silk was dipped in the same solution
of sulphure in alcohol, and a solution of nitro muri-
ate of gold in water was applied •, a white metallic
film was slowly formed, but no other signs of re-
duction were visible.

This experiment was repeated on another bit of
silk with this difference, that the solutions of the
gold and sulphure were both in water, and the white
metallic film was instantly formed, accompanied by a
considerable precipitate of a brown matter.

It is obvious then, that water accelerates, and is
necessary to the appearance of this film : for when
both solutions were in water, it appeared much soon-
er.

EXPERIMENT II.

GOLD.

A piece of silk was immersed in an aqueous solu-
tion of gold, in which the acid predominated, then
a few drops of the aqueous solution of sulphure were
applied ; a white pellicle which looked like silver was
immediately formed, and the silk got a deep brown
colour.

124 REDUCTIONS BY

To another piece of silk dipped in the same solu-
tion of gold, the solution of sulphure in alcohol was
applied, a white metallic film appeared, but not so
evident or so soon as in the preceding experiment,
wherein the solution of sulphure in water was used j
beside the film produced by the aqueous solution of
sulphure was more permanent, and the stain, which
the silk acquired, was more intense, than those pro-
duced by the solution of sulphure in alcohol.

EXPERIMENT III.

SILVER.

I immersed a piece of silk in a solution of the sul-
phure in alcohol, and after most of the spirit evapo-
rated, a solution of nitrate of silver in alcohoi was
applied ; nothing appeared on the silk but a brown
stain. The nitrate of silver used in this experiment
was f jsed, to expel as much water as possible.

Another piece of silk was dipped in the same so-
lution of sulphure ; when most of the alcohol eva-
porated, a solution of crystallized nitrate of silver
in water was applied to the silk, and instantly the
metallic lustre of the silver appeared, attended with
a brown slain.

ALKALINE SULPHURE. J 25

EXPERIMENT IV.

SILVER.

A piece of silk was dipped in the solution of alka-
line sulphure in water, and an aqueous solution of
crystallized nitrate of silver was applied ; the silver
was immediately reduced in greater quantity than in
the preceding experiment, in which the alkaline sul-
phure employed was dissolved in alcohol. The stain
produced in the silk was also more intense.

EXPERIMENT V.

SILVER.

A bit of silk was immersed in a solution of the
sulphure in water, and then a solution of nitrate of
silver in alcohol was applied, but nothing appeared
on the silk, except a brown stain. The nitrate of
silver used in this experiment, was fused, which de-
prived it of a great part of its acid. That this was
the circumstance which prevented the reduction of
the silver, appears from the following experiment.

i

A bit of silk was immersed in the same solution
of silver in alcohol, then some diluted nitric acid-
L 2

126 REDUCTIONS BY

was applied, lastly the aqueous solution of sulphure
was dropped on the silk, and instantly the silver was
restored to its metallic splendour. It is evident then,
that acids contribute to the reduction of silver by
alkaline sulphure, which they effect by promoting
the decomposition of water.

In some time the reduced silver disappears for the
most part, and indeed the white metallic films which
were produced in the experiments on gold, totally
disappeared.

EXPERIMENT VI.

PLATINA.

A bit of silk was immersed in a solution of nitro-
muriate of the ore of platina in distilled water and
dried, then the solution of sulphure in alcohol was
dropped on the silk ; nothing appeared but a brown
stain.

Another bit of silk was dipped in the aqueous so-
lution of sulphure, and a little of the solution of
platina applied; in a short time, a film of reduced
platina appeared.

ALKALINE SULPHURE. 127

To another bit of silk which was dipped in the so-
lution of platina, a few drops of distilled vinegar
were applied, and then the solution of sulphure in
water was added ; a brown stain was immediately
produced, and more platina reduced than in the pre-
ceding experiment.

EXPERIMENT Vli.

MERCURY.

To a bit of silk, which was immersed in a solu-
tion of oxygenated muriate of mercury in water, and
dried in the air, some of the solution of sulphure in
alcohol was applied, but no change, except a light
yellowish brown, was produced.

After the silk was some time exposed to the air,
some very faint shades of black were visible on parts
of it.

To a piece of silk which was immersed in the so-
lution of sulphure in water, some of the same solu-
tion of mercury was applied, immediately the metal
was restored to its metallic lustre in a very striking
manner, and it was remarkable, that the precipitate
on the silk was very small.

128 REDUCTIONS BY

This experiment was repeated with this difference,
that the silk was first wetted with distilled vinegar,
and more of the mercury was reduced than in the
preceding experiment, attended with an olive preci-
pitate, which gradually turned blackish ; the quantity
of precipitated matter in this was much greater than
in the former experiment, but the reduced metal was
not so bright.

EXPERIMENT VIII.

MERCURY.

A bit of silk which was dipped in a solution of ni-
trate of mercury and dried in the air, had no change
produced on it by a solution of sulphure in alcohol,
except a stain compounded of the slate colour, which
the nitrate imparts, and the yellow of the sulphure.

To another bit of silk which was immersed in the
aqueous solution of sulphure, some of the same so-
lution of mercury was applied ; the metal was imme-
diately reduced, and a very black stain attended the
reduction.

ALKALINE SULPHURE. 129

EXPERIMENT IX.

COPPER.

A piece of silk was dipped in a solution of sulphate
of copper and dried in the air, a solution of the sul-
phure in alcohol was applied to it, but no change ex-
cept a brown stain was produced.

To another bit of silk immersed in the aqueous so-
lution of sulphure, some of the same solution of
copper was applied, a white metallic film was slowly
formed, attended with a brown colour.

On another bit cf silk, which was dipped in the
same solution of copper, and placed on a saucer, some
distilled vinegar was dropped, and then a few drops
of the aqueous solution of sulphure were added :
immediately a white metallic film appeared in great-
er quantity than in the preceding experiment.

EXPERIMENT X.

LEAD.

A piece of silk was immersed in a solution of ace-
tite of lead in distilled water, and dried in the air,

130 REDUCTIONS BT

then the solution of sulphure in alcohol was applied,
but nothing appeared on the silk except a brown
stain.

A bit of the same silk was dipped in the same so-
lution of lead, then the solution of sulphure in water
was applied ; the lead was soon reduced to its metal-
lic state ; a brown stain and precipitate of the same
colour attending the reduction.

The same experiment was repeated with this differ-
ence, that the silk was first wetted with distilled vi-
negar, and instantly the lead was reduced of greater
lustre, and in greater quantity, than in the preceding
experiment.

This experiment was tried on a bit of white calico
dipped in distilled vinegar, and placed on the palm
of my hand, and instantly the metallic lustre of the
lead, which was reduced in great quantity, appeared
in a very remarkable manner, attended with a brown
stain.

EXPERIMENT XI.

TIN.

To a bit of siik dipped in a solution of muriate of
tin in distilled water and dried in the air, the solu-

ALKALINE SULPHURE. 131

tion of sulphure in alcohol was applied, nothing ap-
peared but a brown stain.

Another bit of silk was immersed in the solution
of sulphure in water, then the same solution of mu-
riate of tin was applied, in a short time some reduced
tin appeared on the silk. Vinegar promoted the re-
duction of this metal also in a remarkable manner.

EXPERIMENT XII.

ARSENIC.

A bit of silk was immersed in a solution of muriate
of arsenic in distilled water and dried in the air, the
solution of sulphure in alcohol was then applied, the
silk first looked yellow, in a short time the yellow
colour almost entirely disappeared, leaving behind a
whitish precipitate, but no other change was produ-
ced.

Another bit of silk was dipped in the solution of
sulphure in water, then sume of the same solution of
arsenic was applied, a yellow precipitate was formed,
and shortly after this precipitate was surrounded by
a violet margin, but ho other change could be ob-
served.

152 REDUCTIONS BY

I immersed another bit of the same silk in the same
solution of arsenic, some distilled vinegar was then
dropped on it, and lastly the aqueous solution of sul-
phure was applied j after some time a few minute
films of reduced arsenic bright as silver were visi-
ble.

Some attention is necessary to discover the redu-
ced arsenic, as the particles reduced are few, and mi-
nute, and sometimes none can be seen.

EXPERIMENT XIII.

BISMUTH.

To a bit of silk which was dipped in a solution of
nitrate of bismuth in distilled water and dried in the
air, the solution of sulphure in alcohol was applied,
the silk appeared first yellow, then brown, but no
farther change could be observed.

Another bit of silk was immersed in the solution
of sulphure in water, some of the same solution of
bismuth was then applied to it, the metal was imme-
diately reduced, and a brown precipitate was formed.
Vinegar seems neither to promote nor retard the re-
duction.

ALKALINE SULPHURE. 133

Two bits of white calico were dipped in the same
solution of bismuth, to one of these placed on a
saucer some distilled vinegar was added, then a sin-
gle drop of the solution of sulphure in water was ap-
plied, and the whole of the calico except that part on
which the drop fell was covered with reduced bis-
muth, which looked exceedingly bright ; the same
appearance was observed on the other bk, to which
no vinegar was added.

EXPERIMENT XIV.

ANTIMONY.

To a bit of silk which was dipped in a solution of
tartrite of antimony in distilled water and dried in
the air, the solution of sulphure in alcohol was ap-
plied-, the silk got a yellow colour, whose margins
some time after, acquired an orange hue, but no
other change was perceived.

Another bit of the same silk was immersed in the
aqueous solution of sulphure, the same solution of
antimony was then applied, part of the metal was re-
duced, though in small quantity, attended with an
orange precipitate.

The acids of vinegar and tartar seemed to impede
the reduction, the muriatic acid also seemed to have
M

i34) REDUCTIONS BY

the same effete, though not in so great a degree a.s
the two former.

EXPERIMENT XV.

COBALT.

To a bit of silk which was dipped in a solution of
nitrate of cobalt and dried in the air, the solution of
sulphure in alcohol was applied; the silk soon became
brown, but no farther change could be perceived.

To another bit of silk which was immersed in the
solution of sulphure in water, a few drops of the
same solution of cobalt were applied, the silk imme-
diately acquired a dark colour, and in a little time
some of the metal was reduced, attended with a dull
blue precipitate, which changed to a blackish brown.

Muriate of cobalt was reduced in the same man-
ner; vinegar promoted the reduction of both these
preparations of cobalt-

EXPERIMENT XVI.

IRON.

To a piece of silk which was immersed in a solu-
tion of sulphate of iron largely diluted, and dried in

ALKALINE SULPHURE. 135

the air, the solution of sulphure in alcohol was ap-
plied, the silk soon became black, but no other
change could be perceived.

Another bit of silk was dipped in the solution of
sulphure in water, some of the same solution of iron
was then applied, the silk instantly assumed a black
colour, but no reduced iron appearing, it was immer-
ged in a glass of water, and transferred a bright film
of reduced iron to the surface of that fluid.

Sometimes part of the film has not the metallic
lustre, which is very evident in other parts of it, so
that the parts completely reduced can be easily dis-
tinguished from the dull and imperfectly reduced
black oxid of iron, intermixed with these bright
films.

The same experiments were repeated on bits of
calico with the same result, the calico from its spon-
gy texture is better suited to produce strong films
than silk is.

Vinegar did not promote the reduction of iron in
these experiments.

136 REDUCTIONS B1

EXPERIMENT XVIfc

ZINC.

To a bit of ?ilk which was immersed in a largely
diluted solution of muriate of zine, and dried in the
air, some of the solution of sulphure in alcohol was
applied, nothing ..ppeared on the silk, but the yellow
colour which the solution of sulphure imparts.

Another bit of silk was dipped in the solution of
sulphure in water, and some of the same solution of
zinc was applied, the yellow colour which the solu-
tion of sulphure gave the silk soon became white ;
but no reduced zinc could be seen. The silk was
then immerged in a glass of clear water and transfer-
red a bright film of reduced zinc to its surface.

In another experiment made with white calico, the
pellicle transferred to the surface of water was bright-
er, and more zinc was reduced than in the preceding
experiment.

Sulphate of zinc also was reduced both on silk and
calico, with this difference, that black and olive pre*-
eipitates attended the redu&ion,

ALKALINE SULPHURE, 137

EXPERIMENT XVIIi

MANGANESE.

I dipped a bit of silk in a diluted solution of ni-
trate of manganese, and dried it in the air, the solu-
tion of sulphure in alcohol was then applied, the silk
acquired a yellow colour which soon disappeared,
but no other change eculd be observed.

To another bit of silk, which was immersed in the
solution of sulphure in water, a drop of the same so-
lution of manganese was- applied, instantly a pearl-
white precipitate was formed, the margin of which
soon acquired a bright film of reduced manganese.
Under this film a violet tinge was evident;

The nitrate of manganese used in this experiment
was very acid.

A solution of alkaline sulphure in water after a cer-
tain length of time loses the power of reducing the
metals, in which respect it resembles an old solution
of sulphate of iron.

M2

138 REDUCTIONS BY

Having procured a more neutral solution of nitrate
of manganese, I immersed a bit of silk in the solu-
tion of sulphure in alcohol, when most of the spirit-
evaporated; a single drop of this solution of manga-
nese was applied, instantly a bright film of reduced
manganese appeared, attended with a violet tinge,
and a brown precipitate. After some time the violet
tinge disappears.

On another bit of silk immersed in the same solu-
tion of sulphure in alcohol, a drop of a solution of
sulphate of manganese in distilled water was applied,
instantly films of reduced manganese bright as silver
appeared, accompanied with a faint violet tinge, and
a pearl-white precipitate. These films soon disap-
pear.

A solution of alkaline sulphure in alcohol does not
by age lose its power of reducing the metals, as that
in water does ; I kept the former solution more than
two years, and found it at the end of that time as
capable of reducing the metals, as when it was made.

It is manifest from the experiments related in this
chapter, ■

1. That water is essential to the reduction of me*
tals by alkaline sulphure.

ALKALINE SULPHURE. 133

2. That alcohol does not promote these reductions
without the aid of water.

3. That alkaline sulphure does not reduce the me-
tals by giving them phlogiston, nor by uniting with,
and separating their oxygen, for were either of these
opinions true, a solution of alkaline sulphure in al-
cohol should reduce them as effectually as a solution
of the same in water does.

4. That acids contribute to these reductions by«
promoting the decomposition of water.

Now since M. Gengembre has demonstrated, that-
water is decomposed by alkaline sulphure, who can
doubt that it is decomposed in these reductions ?

The manner in which metals are reduced by this
substance, seems to be the following.

An hydrure of sulphur, that is, a combination of
hydrogen and sulphur is formed: this hydrure of sul-
phur attracts the oxygen of the water, while the hy-
drogen of the latter unites in its nascent state, with
the oxygen of the metal, and reduces it.

The experiments in this chapter leave us no room
to doubt of the decomposition of water in metallic
reductions by alkaline sulphure, and serve to illustrate

140 REDUCTIONS BY

and confirm the manner in which sulphur, phospho-
rus, and other combustible bodies, effect the reduc-
tion of metals.

SULPHURATED HYDROGEN CAS. Ml

CHAPTER V.

REDUCTION OF METALS

BY

SULPHURATED HYDROGEN GAS.

HAVING treated of the effects of hydrogen gas
and sulphur separately, I shall next treat of their
effects, when combined in the form of sulphurated
hydrogen gas.

I obtained this elastic fluid by pouring water, aci-
dulated with sulphuric acid on alkaline sulphure,
prepared in the manner mentioned in the preceding

14-2 REDUCTIONS BY

chapter ; but had it been prepared with a caustic al-
kali, it is probable the gas would be more powerful.
The sulphure of the shops is generally unfit for
these experiments.

It is necessary in experiments with sulphurated
hydrogen gas, hydrogen gas, &c. to have some mode
of conveying them into a chimney, as they ^re of-
fensive and unwholesome.

EXPERIMENT I.

GOLD.

A piece of silk, which was immersed in a solution
©f nitro-muriate of gold in water, and dried in the
air, was exposed to sulphurated hydrogen gas, the
silk got a slight tinge of brown, but no other change
occurred •, it was then wetted with alcohol, and after
some time, the brown became more intense, and
white films appeared on some parts of the silk, ow-
ing to moisture collected from the gas, which is al-
ways replete with water.

Another bit of silk was dipped in the same solu-
tion of gold and exposed, while wet, to the gas j
the yellow colour, which the solution of gold gave
the silk ; was immediately changed to a brown, and a

SULPHURATED HYDROGEN GAS. 143

white metallic pellicle appeared, and covered the
whole surface of the silk opposed to the gas ; but no
purple or other colours, that usually attend the re-
duction of this metal by other agents, could be per-
ceived. This pellicle did not entirely disappear as
the silk became dry ; though it lost most of its lustre
rind looked more like silver, or some other white
metal imperfectly reduced, than gold.

This elastic fluid, and alkaline sulphure, have an
efFect on the reduction of gold, very different from
that of the vapour of sulphur obtained from a burn-
ing match, which further appears from the follow-
ing experiment, made with sulphurated hydrogen
gas, that happened to be mixed with some sulphur-
ous acid gas.

EXPERIMENT II.

GOLD.

A piece of silk, which was dipped in a solution
of gold in ether and dried in the air, was exposed
to a current of sulphurated hydrogen gas, containing
some sulphurous acid gas ; but no signs of reduction
could be perceived : the silk was then wetted with
alcohol, still no visible change was produced, except
a brown stain where the alcohol most abounded;

144) REDUCTIONS B*

this stain, after some minutes exposure to atmosphe-
ric air, was covered with a white metallic film, which
soon disappeared; after some minutes the silk was
wetted with water and exposed again to the gas, a
white metallic film immediately appeared, and the
brown stain began to change slowly to a purple ; the
silk was soon covered with various colours, as blue,
red, and orange, and some spots of reduced gold of
its own proper colour appeared ; after some time the
white film and all the colours, except the purple, dis-
appeared, some specks of the perfectly reduced gold
were permanent.

Another bit of silk, which was immersed in an
aqueous solution of gold and exposed to the same
.mixed gas, exhibited nearly the same appearances.

EXPERIMENT III.

GOLD.

Having found that sulphurated hydrogen gas had
a powerful effect in reducing other metals, I was de-
sirous of trying its effects on a larger scale, thinking
it might be attended with more success ; I therefore
immersed a quarter of a yard of silk in an aqueous
solution of gold and exposed it while wet, to this
gas in close vessels ; the silk was soon covered with

SULPHURATED HYDROGEN GAS. 14'5

a white metallic pellicle, which disappeared in a short
time: the experiment was continued about twelve
hours, and on withdrawing the silk from the gas, I
could not perceive the smallest vestige of reduced
metal, or purple, or other colours, that constantly
attend the reduction of gold.

The silk had a dull brown hue verging on a slate
colour.

EXPERIMENT IV.

SILVER.

A piece of silk, which was immersed in a solu-
tion of nitrate of silver in water, and dried in the
air, was exposed to a current of sulphurated hydro-
gen gas, but no change could be perceived for some
time •, at length, when the silk collected moisture
from the gas, some particles of reduced silver were
visible, accompanied by a brown stain.

Another piece of silk was dipped in the same so-
lution of nitrate of silver, and exposed while wet,
to the gas ; the silver was instantly reduced all over
the side of the silk opposed to the current, a great
variety of beautiful colours, as red, orange, yellow,
green, and blue, attended the reduction ; most of
N

146 REDUCTIONS BY

these disappeared, but part of the silver remained
permanently reduced.

I found that, if the silk be immersed in a solution
of silver in alcohol and dried, and then moistened
with water, and exposed while wet to the gas, none
of these colours appear.

This experiment was repeated on a quarter of a
yard of silk in close vessels, and immediately both
sides of the silk were covered with reduced silver,
attended with the same beautiful colours; the silk
was left exposed to the gasseven or eight hours, and
being then examined, no reduced silver could be
seen ; nothing remained but a strange medley of co-
lours, chiefly blue, green, purple, and orange, un-
equally mixed, some prevailing more than others in
certain parts of the silk •, however, the die is by no
means disagreeable.

EXPERIMENT V.

SILVER.

A piece of silk, which was immersed in a solu-
tion of fused nitrate of silver in alcohol, and dried
in the air, was exposed to a current of the gas ; but
no change could be perceived for some time : it was

SULPHURATED HYDROGEN GAS. 147

then wetted with alcohol, still no alteration could be
observed, till the silk attracted moisture from the
gas, when small particles of reduced silver began to
appear, attended with a brown stain.

If the silk immersed in the solution of silver in
alcohol, and exposed while wet to the gas, be kept
constantly wet with alcohol, these appearances take
place sooner.

A piece of silk, which was dipped in a solution
of muriate of silver in ammonia, and exposed, while
wet, to the gas, had in a short time its surface co-
vered with reduced silver ; but another piece of silk
dipped in the same solution of silver and dried, un-
derwent no such change.

EXPERIMENT VI.

PLATINA.

A bit of silk, which was dipped in a solution of
nitro-muriate of the ore of platina in distilled water
and dried in the air, was exposed to a current of sul-
phurated hydrogen gas j but underwent no percepti-
ble change.

148 KCTH T CTIONS BY

Another bit of si k was immersed in the same so-
lution of platina and exposed while wet, to the gas j
the whole surface of the silk, opposed to the current,
was instantly covered with reduced platina, which
soon lost its lustre; nothing remaining but a brown
colour, with some faint vestiges of the reduced me-
tal.

This experiment was repeated on a bit of linen
with the same result.

EXPERIMENT VII

MERCURY.

A hit of silk, whirh was dipped in a solution of
oxygenated muriate of mercury in distilled water,
and dried in the sir, was exposed to a current of the
gas ; the only visible change produced was a slight
shade of yellow on part of the silk.

Another bit of silk was immersed in the same so-
lution of mercury and exposed, while wet, to the
gas ; the mercury was immediately reduced, but soon
lost its lustre ; the gas reacting changed most of it to
a substance of a dull white colour.

SULPHURATED HYDROGEN GAS. 149

The same experiments were made with nitrate of
mercury, with the same result.

EXPERIMENT VIII.

COPPER.

A bit of silk was immersed in a solution of sul-
phate of copper in distilled water, and suspended in
the air to dry ; it was then exposed to a current of
the gas, the silk assumed a brown colour; but no
other change appeared.

Another bit of silk was dipped in the same solu-
tion of copper, and exposed while wet to the gas, a
white metallic film attended with a brown stain, im-
mediately appeared, some parts had a yellow film ap-
proaching to the colour of copper ; these films all
disappeared leaving behind a brown stain •, the parts
which were covered with the yellow film resembling
copper, exhibited after some time, a dull bluish dis-
agreeable matter.

EXPERIMENT IX.

LEAD.

Having dipped a piece of silk in a solution of ace-
tite of lead in distilled water and dried it in the air,
N 2

150 REDUCTIONS BY

I exposed it to a stream of the gas ; the silk became
a little brown, but no other change could be obser-
ved.

Another bit of silk was immersed in the same so-
lution of lead, and exposed while wet to the gas; no
sooner did it touch the silk, than a brown tinge dif-
fused itself like a passing shadow over the whole sur-
face of the silk, accompanied with a bright coat of
reduced lead, whieh resembled silver.

The brown tinge, which the silk acquires, resem-
bles what happens when white paper is slightly singed
by holding it near a burning body.

This experiment was repeated on a quarter of a
yard of silk in close vessels, and the silk was imme-
diately covered with a coat of reduced lead, which
had the brilliance of silver, and was attended with a
brown tinge ; the experiment was continued several
hours, after which the silk was examined, and found
to have lost all the argentine lustre, which was suc-
ceeded by a sparkling gray die ; a sulphure of lead,
or galena, being formed in the fibres of the silk.
The same experiment was repeated on two other
pieces of silk with the same result.

This elastic fluid is so powerful a reducer of the
metals, that if chambers painted with white lead,

SULPHURATED HYDROGEN GAS. 15i

have any considerable degree of moisture, and are
exposed to its influence, the lead on the surface of
the walls is reduced, and that chiefly where the hu-
midity is most abundant -, this effect I observed, was
produced, even at the distance of three chambers
from the place where the gas was formed ; and the
lead was reduced most evidently behind the window
shutters where the moisture of the wall was most
considerable.

It is a common experiment with chymists, in order
to shew the effects of this gas, to draw characters
with a solution of sugar of lead on paper, which they
place over a glass of water containing some alkaline
sulphure ; in some time the characters drawn on the
paper acquire a brown, or black colour, and become
visible ; which amuses the spectators.

But it is surprising, that the metal has never been
reduced in this experiment even by chance ; and not
less so, why lead should be singled out for this trial
of skill, in preference to other metals, which are
equally affected by this gas.

152 REDUCTIONS B*

EXPERIMENT \.

TIN.

A piece of silk was dipped in a solution of muriate
of tin in distilled water and dried in the air; the silk
on exposure to a current of the gas, scarce under-
went any change, except a few brown specks disper-
sed over its surface.

Another bit of silk was immersed in the same so-
lution of tin, and exposed while wet to the gas, which
no sooner touched the silk, than the surface opposed
to the current was covered with reduced tin of great
brightness ; in some time various colours, as blue,
orange, and a faint purple, appeared, and became
more evident, as the reduction proceeded.

The gas does not re- act. on this metal so much as
on mercury, and some other metals, part of the re-
duced tin remained permanent, but most of it disap-
peared, and left behind a disagreeable brown stain.

?WLPHURATED HYDROGEN CAS. 153

EXPERIMENT Xt.

ARSENIC.

A bit of silk was immersed in a solution of muri-
ate of arsenic in distilled water and dried in the air,
it was then exposed to a stream of sulphurated hy-
drogen gas, but no change could be observed, ex-
cept a faint tinge of citron yellow, which appeared
on some parts of the silk.

Another bit of silk was dipped in the same solu-
tion of arsenic and exposed while wet to the gas, the
arsenic was instantly reduced all over the surface, op-
posed to the gas, attended with a citron yellow co-
lour.

The gas soon re-acted on the reduced arsenic ;
and nothing remained but the yellow stain.

EXPERIMENT XII.

BISMUTH.

I dissolved some bismuth in nitric acid, and evapo-
rated the solution to dryness, the salt was then dis-

154 DEDUCTIONS BY

solved in distilled water, and the solution deposited
a copious white precipitate, but retained a quantity
of the metal sufficient for these experiments.

In this solution of bismuth a piece of silk was im-
mersed, and dried in the air, it was then exposed to
a stream of the gas, and the only visible effect pro-
duced was a very faint tinge of brown.

Another bit of silk was dipped in the same solu-
tion of bismuth, and exposed wet to the gas, the silk
was instantly covered with a bright pellicle of redu-
ced bismuth, which soon lost most of its metallic
lustre, being changed by the reaction of the gas to
a sulphure.

Mr. Kirwan in his experiments on hepatic air,
found that nitrous solution of bismuth, by mixture
with a solution of hepatic air in water, changes to
a reddish brown, and even assumes a metallic ap-
pearance.

He also found that nitrates of silver, lead, and ace-
tite of lead, were precipitated black.

SULPHURATED HYDROGEN GAS. 155

EXPERIMENT XIII.

ANTIMONY.

A piece of silk, which was immersed in a solution
of tartrite of antimony in distilled water and dried
in the air, was exposed to a stream of the gas, but suf- .
fered no visible change, except that a few specks of
yellow and orange appeared.

A bit of silk was dipped in the same solution of
antimony, and exposed while wet, to the gas, the
antimony was immediately reduced to its metallic
form, attended with a deep orange colour ; in some
time, most of the metallic lustre disappeared, a few
specks only remaining permanent.

EXPERIMENT XIV.

IRON.

A piece of silk was immersed in a diluted solution
«f sulphate of iron in distilled water and dried ; it
was then exposed to a current of the gas, but under-
went no visible change.

156 REDUCTIONS BY

Another bit of silk was dipped in the same
solution of iron and exposed while wet, to the gas ;
the silk soon began to acquire a dark colour, which
gradually increased, and at length became black, at-
tended with an obscure metallic film. The silk was
immersed in water, and deposited a bright metallic
film on the surface of that fluid.

EXPERIMENT XV.

ZINC.

A bit of silk which was immersed in a diluted so-
lution of sulphate of zinc in distilled water and dried
in the air, was exposed to a current of the gas, but
underwent no visible change.

Another bit of silk was dipped in the same solutioa
of zinc and exposed while wet, to the gas, but no
change in the colour of the silk, or sign of reduction
could be perceived ; the silk was then immerged in
a glass of clear water, and transferred to its surface
a bright metallic film of the colour of zinc.

When a languid stream of gas was employed in
these experiments the films transferred to water
were scarce visible.

SULPHURATED HTDROGEN GAS. 157

Experiment xvi.

ZINC.

A piece of silk, which was immersed in a largely
^diluted solution of muriate of zinc and dried in the
air, was exposed to a brisk current of sulphurated
hydrogen gas, but underwent no visible alteration.

Another bit of silk was dipped in the same solu-
tion of zinc, and exposed while wet, to the same brisk
current of gas ; instantly the surface of the silk op-
posed to the gas, was covered with a bright coat
of reduced zinc, attended with faint orange and
purple colours.

Though the reduced zinc was quite evident, yet
I had the curiosity to examine its appearance on the
surface of water ; I therefore immersed the silk in a
glass of that fluid, and a bright metallic pellicle,
which retained the texture of the silk, as wax re-
tains the impression of a seal, was transferred to its
surface.

Another bit of silk, dipped in the same solution
of zinc, and exposed for a longer time to the gas,
O

158 DEDUCTIONS BY

lost its metallic lustre, the zinc being changed to a
sulphure by the re-acYion of the gas.

These experiments, on sulphate and muriate of
zinc, show that the acid in which the metal is dissol-
ved, influences the reduction in a remarkable man-
ner.

It is evident from the experiments related in this
chapter,

1. That water is essential to the reduction of me-
tals by sulphurated hydrogen gas.

2. That alcohol does not promote these reductions
without the aid of water.

3. That sulphurated hydrogen gas does not re-
duce the metals by giving them phlogiston, nor by

ng with and separating their oxygen; for, were
of these opinions well founded, metallic solu-
rohol should be as effectually reduced by
this gas, as metallic solutions in water are.

n we consider that alkaline sulphure reduces

the metals by d ng water, we have everv rea-

■■' hurated hydrogen gas re-

ihem in the same manner, bince the same cir-

SULPHURATED HYDR0CEN GAS. 159

cumstances are necessary to both ; the hydrure of
.sulphur, which constitutes the base of this gas at-
tracts the oxygen of the water, while the hydrogen
of the latter unites in its nascent state, with the
oxygen of the metal, and reduces it.

Hence it follows, that the hydrure of sulphur is
oxygenated by the oxygen of the water, while the
metal is restored to its combustible state.

PHOSPHORATED HYDROGEN GAS. 161

CHAPTER VI,

REDUCTION OF METALS

BY

PHOSPHORATED HYDROGEN GAS.

THE effects of hydrogen gas and phosphorus on
the reduction of metals in the fibres of silk have
been treated of separately in the two first chapters;
in this, I shall briefly treat of their effects, when com-
bined in the form of phosphorated hydrogen gas,
which from its high degree of inflammability seemed
■well adapted to this purpose.
02

162 REDUCTIONS BY

The spontaneous inflammation of this kind of air
was known to M. Gengembre in 1783, and his ex-
periments were published in Rosier's journal for
October 1785.

Mr. Kirwan also, without any knowledge of M.
Gengembre's experiments, discovered the same air,
which he calls phosphoric air ; and published his ex-
periments in the 76th volume of the Philosophical
Transactions for 1786.

This elastic fluid may be obtained by digesting a
solution of potash in water with about half its weight
of phosphorus in a heat sufficient to melt the latter,
and may be received in glass vessels over mercury.

But finding it inconvenient to introduce pieces of
silk prepared for these experiments over mercury in
close vessels, I exposed them to the gas, as it issued
from the neck of the phial in which it was prepa-
red.

Part of this elastic fluid is spontaneously inflam-
mable, but the other has not that property, which
M. Gengembre imputes to the presence of carbonic
acid ; for the sake of brevity, I shall designate the lat-
ter bv the term gas, or phosphorated hydrogen gas ; and
the former by the epithets spontaneously inflammable, or
detonating gas, which I found does not burn or scorch
silk wetted with metallic solutions.

rHOPHORATED HYDROGEN GAS. 16*3

EXPERIMENT I.

GOLD.

A piece of silk, which was immersed in a solution
of nitro-muriate of gold in distilled water, and sus-
pended in the air twelve hours to dry, was divided into
three parts.

One of these was exposed to a stream of phospho-
rated hydrogen gas : the silk became brown, and its
margins, which happened to touch the sides of the
phial, acquired a violet tinge : but no reduction took
place.

Another of these parts was wetted with alcohol,
and exposed to the gas ; but no signs of reduction
could be perceived.

The remaining part was wetted with water, and
was no sooner exposed to the gas, than the reduction
commenced over the whole silk, which was soon co-
vered with a bright coat of reduced gold.

16-i REDUCTIONS BY

EXPERIMENT II.

SILVER.

A piece of silk was dipped in a solution of fused ni-
trate of silver in alcohol, and dried in the air : it was
then divided into three parts.

One of these, in order to dissipate moisture more
effectually, was dried still better by a gentle heat,
and exposed to the gas ; the silk acquired a brown-
ish dark colour : but no other alteration could be
perceived.

Another of these parts, which was also better dri-
ed by a gentle heat, was wetted with alcohol, and ex-
posed to the gas : the silk acquired a dark brown co-
lour ; but no other change could be observed.

The remaining part was wetted with water, and
exposed to the gas : the reduction commenced im-
mediately, and in a short time the silk was covered
with reduced silver.

PHOSPHORATED HYDROGEN GAS. 16.0

EXPERIMENT III.

PLATINA.

A piece of silk was immersed in a solution ot
nitro-muriate of the ore of platina in distilled water,
and dried in the air 5 it was then divided into three
parts.

One of these parts was exposed to the gas j but
-suffered no visible change.

Another of them was wetted with alcohol, and ex-
posed to the gas*, but underwent no perceptible
change.

The remaining part was wetted with water, and
exposed to the gas : in about three or four minutes,
a bright metallic film, of great lustre, appeared on the
side of the silk, opposed to the gas.

Another bit of silk, which was dipped in the same
solution of platina, and exposed, while wet, to the
spontaneously inflammable gas, was immediately co-
vered with reduced platina, which being transferred

166 REDUCTIONS BY

to the surface of water, looked bright as silver, and
retained the impression of the silk.

EXPERIMENT IV.

MERCURY.

A bit of silk, which was immersed in a solution of
nitrate of mercury in distilled water, and dried in
the air, was exposed to the gas ; but underwent no
visible change.

Another bit of silk was dipped in the same solu-
tion of mercury, and dried : it was then wetted with
alcoaol, and exposed to the gas j but no sign of re-
duction appeared.

Another bit of silk was immersed in the same solu-
tion of mercury, and exposed to the gas ; the metal
was instantly reduced all over the silk ; a great vari-
ety of beautiful colours attending.

A piece of silk was dipped in a solution of oxyge-
nated muriate of mercury in distilled water, and dried
in the air : it was then divided into two parts.

One of these was exposed to the gas : no change
appearing, it was wetted with alcohol, and exposed

PHOSPHORATED HYDROGEN GAS. 167

again to the gas •, but still no alteration could be per-
ceived.

The remaining part was wetted with water, and
was no sooner exposed to the gas, than the mercury
was reduced over the whole silk. No colours attend-
ed the reduction.

Mr. Kirwan introduced some precipitate per se to
a small portion of phosphoric air: the precipitate
soon grew black, and a white smoke appeared ; in
two days the precipitate remained solid, yet acquired
a pale white colour like that of steel : the air lost its
spontaneous inflammability *

EXPERIMENT V.

COPPER.

A piece of silk, which was immersed in a solution
of sulphate of copper in distilled water and dried in
the air, was divided into two parts.

One of these was exposed to the gas, but no visi-
ble change occurred.

* M. K iw."n. Phil. Tram, for 1786.

168 REDUCTIONS BY

The remaining part was wetted with water and
exposed to the gas, in a few minutes a brownish mat-
ter appeared in the silk, but nothing metallic could
be seen ; the silk was then dipped in a glass of clear
water, and transferred a small white metallic pellicle
to its surface.

In another experiment made with the spontane-
ously inflammable gas, a white metallic pellicle was
immediately formed, attended with a brown stain j
this pellicle resembled silver or a white metal ; but
the gas soon re-acted on it, and formed a disagreeable
brown matter in the fibres of the silk.

EXPERIMENT VI.

LEAD.

A bit of silk, which was dipped in a solution of
acetite of lead in distilled water and dried in the air,
was exposed to the gas, but suffered no visible
change.

Another bit of silk was immersed in the same so-
lution of lead, and exposed while wet to the gas, but
nothing metallic could be seen ; the silk, however,
©n immersion in water, transferred a few minute
Wright films to the surface of that fluid.

PHOSPHORATED HYDROGEN GAS. 169

In another experiment made with the detonating
gas, the reduced films were more evident.

EXPERIMENT VII.

TIN.

A bit of silk, which was dipped in a solution of
muriate of tin in distilled water and dried in the air,
was exposed to the action of the gas without suffer-
ing any visible alteration.

Another piece of silk was immersed in the same
solution of tin and exposed while wet to the gas, but
no signs of reduction could be perceived ; the silk
was then immersed in water and transferred a deli-
cate metallic film to its surface.

EXPERIMENT VIII.

ARSENIC.

A bit of silk, which was immersed in a solution of
muriate of arsenic in distilled water and dried in the
air, was exposed to the gas, but no change could be
perceived.

170 REDUCTIONS BY

Another bit of silk, immersed in the same solution
of arsenic and exposed while wet to the gas, acquired
in a few minutes a brown stain, but nothing metallic
could be seen on the silk ; which, however, on being
dipped in water, transferred a very minute film of re-
duced arsenic to its surface.

In another experiment made with the detonating
gas, the films of reduced arsenic were much more
evident, of greater brilliance and attended with a
brown stain produced in the fibres of the silk.

EXPERIMENT IX.

BISMUTH.

A piece of silk, which was dipped in a solut on of
nitrate of bismuth in distilled water and dried in the
air, was exposed to the gas but no alteration could be
observed.

Another bit of silk was immersed in the same so-
lution of bismuth, and exposed while wet to the gas ;
the silk in two or three minutes got a brown stain,
which gradually became more intense, and a very de-
licate metallic film appeared ; the silk was then im-
merged in water, and transferred a bright film of re-
duced bismuth to the surface of that fluid -, the film
retained the impression of the silk.

PHOSPHORATED HYDROGEN GAS. 1*71

EXPERIMENT X.

ANTIMONY.

A bit of silk immersed in a solution of tartrite of
antimony in distilled water and dried in the air was
exposed to the gas, but suffered no apparent change.

Another piece of silk was dipped in the same so-
lution of antimony, and exposed while wet to the
gas, but no signs of reduction appeared ; the silk was
then immerged in water, to the surface of which it
transferred one small spangle.

This experiment was repeated with the detonating
gas, which with difficulty produced some sparkling
films ; the silk was immersed in water and transfer-
red the films to its surface.

A white matter was visible in the fibres of the
silk.

372 REDUCTIONS B\

EXPERIMENT XI.

COBALT.

A piece of silk immersed in a solution of muriate
of cobalt and dried in the air, was exposed to the gas,
but suffered no visible alteration.

Another bit of silk was dipped in the same solu-
tion of cobalt, and exposed while wet to the gas, but
no sign of reduction appeared j nor did the silk
transfer a film to water.

Another bit of silk was immersed in a solution of
nitrate of cobalt, and exposed while wet to the deto-
nating gas, no signs of reduction were visible for some
time ; but at length a few small spangles of the me-
tal appeared on the silk, and were very brilliant,
and when transferred to water were still more so ; a
white matter could be seen in the fibres of the silk.

EXPERIMENT XII.

IRON.

A bit of silk was immersed in a largely diluted so-
lution of sulphate of iron in distilled water, and dried j

PHOSPHORATED HYDROGEN GAS. 173

it was then exposed to the action of the gas •, but no
alteration could be perceived.

Another bit of silk was dipped in the same solution
of iron and exposed while wet to the gas, in a few
minutes some parts of the silk acquired a light brown
colour ; but no reduced iron could be seen on the silk,
which however, transferred a very minute and deli-
cate film to water.

This experiment was repeated with a strong deto-
nating gas, and a very brilliant metallic film about
four lines in diameter was reduced on the silk, ac-
companied with a brown stain, but nothing like the
black oxid of iron appeared.

EXPERIMENT XIII.

ZINC.

A bit of silk, which was immersed in a largely
diluted solution of muriate of zinc was exposed dry
to the gas, but underwent no visible alteration.

Another piece of silk was dipped in the same so-
lution of zinc and exposed wet to the gas ; no signs
of reduction appearing, the silk was immerged in
water, and left a very minute metallic film on its sur-
face, which could with difficulty be seen.
P2

174 REDUCTIONS BY

The experiment was repeated*with the detonating
gas, and a very bright metallic film of zinc, four or
five lines in diameter, was reduced on the silk.

This experiment succeeded also with a largely di-
luted solution of sulphate of zinc.

The silk, viewed by transmitted light, exhibited
a brown stain beneath these films of iron and zinc.

The experiments detailed in this chapter shew,

1. That water is essential to the reduction of me-
tals by phosphorated hydrogen gas.

2. That alcohol does not promote these reduc-
tions without the aid of water.

3. That this elastic fluid does not reduce metals
by giving them phlogiston, nor by combining with,
and separating their oxygen ; for, were either of
these suppositions true, it should reduce them as well
with alcohol as with water.

After explaining the manner, in which sulphurated
hydrogen gss reduces the metals, the mode of agency
of phosphorated hydrogen gas is sufficiently obvi-
ous.

PHOSPHORATED HYDROGEN GAS. 175

The gas attracts the oxygen of the water, while
the hydrogen of the latter unites in its nascent state
with the oxygen of the metal and reduces it.

Hence it follows that the hydrure of phosphorus,
which constitutes the base of this gas, is oxygenated
by the oxygen of the water, while the metal is, at
the same time, restored to its combustible state.

By hydrure of phosphorus, is meant a combina-
tion of hydrogen and phosphorus, containing less
caloric than is necessary to the gaseous state.

CHARCOAL.

177

CHAPTER VII.

REDUCTION OF METALS

BY

CHARCOAL.

FINDING several combustible bodies, as hydro-
gen, phosphorus, sulphur, and combinations of these,
capable of reducing the metals in the ordinary tem-
perature of the atmosphere ; I was desirous of know-
ing if charcoal also possessed that power.

Charcoal may be applied with this view in several
forms. M. Rouelle has observed that caustic fixed
alkali dissolves a considerable quantity of this sub-
stance.

178 REDUCTIONS BY

Charcoal also exists in a very attenuated state in
ether, alcohol, gum, &c,

1 have examined some of its effects on the reduc-
tion of metals, in these different forms, in which it
probably exists combined with hydrogen, and also
some of its effects in the solid form.

EXPERIMENT I.

GOLD.

A small bit of well burned charcoal was suspended
by a thread in a phial containing a diluted solution
of nitro-muriate of gold in distilled water ; some air
bubbles soon appeared on the charcoal ; and in about
two hours reduced gold was. evident on its lower sur-
face, and increased gradually, till the charcoal was
nearly coated with gold of its proper colour.

This experiment was repeated with a richer solu-
tion of gold ; the reduction did not commence near
so soon, nor was the quantity reduced so great, or
brilliant, as in the preceding experiment.

CHARCOAL. 179

EXPERIMENT II.

GOLD.

A small bit of charcoal was suspended in a solu-
tion of gold in ether : an effervescence immediately
commenced, and continued for a considerable time :
but the solution suffered no change of colour, nor
was there a particle of the gold reduced.

I should not be surprised if the gold were reduced
in this experiment, as charcoal contains a large quan-
tity of water, which it powerfully attracts from the
surrounding air : however not a vestige of reduced
gold could be perceived.

Bits of charcoal were suspended in the same man-
ner in most of the metallic solutions treated of in
this essay : no change was perceived on those im-
mersed in solutions of arsenic, manganese, and fused
nitrate of silver in water: but a bit immersed in a
solution of the same nitrate in alcohol, had parts of
it covered with bright sparkling particles, which
seemed to vegetate from the charcoal, and were evi-
dently reduced silver : for they were not soluble in
watei , on the surface of which the bit of charcoal
deposited some small spangles of great lustre. The

180 REDUCTIONS BT

bits immersed in solutions of sulphate of iron and zinc
exhibited some very faint signs of reduction.

But these experiments were not repeated, nor suffi-
ciently varied, to enable us to form a just opinion of
the power of charcoal in reducing metals in this way.

A small quantity of charcoal, reduced to fine pow-
der, was digested several days in a strong solution of
caustic potash in alcohol ; the phial was frequently
shaken to promote the solution.

Some of the clear solution, which was of a reddish
colour, was poured into a phial for use.

EXPERIMENT III.

GOLD.

A few drops of this solution of charcoal, or car-
bon, were applied to a bit of silk ; after the alcohol
evaporated, a solution of gold in ether was dropped
on, and immediately produced a brown, which, in
about half an hour, was changed to a purple hue,
owing to water attracted from the air j but no other
sign of reduction appeared.

Another bit of silk was immersed in the solution
of carbon, and when the alcohol evaporated, a few

CHARCOAL. 181

drops of an aqueous solution of gold were applied •, a
brown stain was instantly formed •, the silk was kept
wet with water ; the stain gradually assumed a pur-
ple tinge, and in about five minutes, some reduced
gold of its proper splendour and colour appeared:
and in some time after every part of the silk,
to which the solutions of carbon and gold were ap-
plied, was coated with reduced gold, which remained
permanent. During the experiment, it is necessary
to keep the silk constantly wet with water.

If the solution of gold be applied before the alco-
hol evaporates, a black precipitate is formed, along
with the brown stain. In an experiment made in
this manner, a metallic film, whitish and obscure, ap-
peared in the beginning ; but soon vanished : and in
some time after, the gold was reduced of its proper
colour ; and a speck of ruby red appeared on the
margin.

The silk viewed by transmitted light presented va-
rious colours, as purple, blue, and some green.

EXPERIMENT IV.

SILVER.

A few drops of the solution of carbon were ap-
plied to a bit of silk : when the alcohol evaporated,

Q

182 REDUCTIONS BY

a solution of fused nitrate of silver in alcohol was ap-
plied : alight brown stain was immediately produced
in the silk ; but no reduced silver could be seen.

The solution of carbon was applied to another bit
of silk, and when the alcohol evaporated, an aqueous
solution of fused nitrate of silver was dropped on :
a brown stain was instantly formed, and in about ten
minutes, minute films of reduced silver were visible.

The silk was kept wet with water during the expe-
riment ; and the brown stain was gradually changed
to black. In some little time the metallic films dis-
appeared.

If the solution of silver be applied to the silk, be-
fore the alcohol evaporates, black and brown precipi-
tates are immediately formed ; and commonly no re-
duced silver can be seen ; but sometimes very minute
films appear.

EXPERIMENT V.

PLATINA. .

To a bit of silk, which was immersed in a solution
of nirro muriate of platina in distilled water, and
dried in the air, a few drops of the solution of car-

CHARCOAL.

I!

bon were applied ; but no visible change was pro-
duced.

Another bit of silk was dipped in the solution of
carbon, and when the alcohol evaporated, a few drops
of the solution of platina were applied : a yellow pre-
cipitate was immediately formed, and in about ten
minutes delicate films of reduced platina were visible:
these metallic films soon vanished •, and nothing but a
yellow stain and the precipitate remained.

A bit of calico, on which this experiment was re-
peated, transferred a bright film of reduced platina
to the surface of water.

During these experiments, the silk and calico were
kept wet with water.

LXl'ERIMENT VI.

MERCURY.

On a bit of silk, which was immersed in a solu-
tion of oxygenated muriate of mercury in distilled
water and dried in the air, a little of the solution of
carbon was dropped, but the silk underwent no vi-
sible change.

18i REDUCTIONS B*

Another bit of silk was dipped in the solution of
carbon, and when the alcohol evaporated, a little,
of the same solution of mercury was applied, a yel-
low precipitate was immediately formed, and soon
after small films of reduced mercury appeared on the
margin of the stain.

This experiment was repeated with a solution of
nitrate of mercury, and the reduction of the metal
was very evident on the margin of the stain, which
was black ; the precipitate on the bit of silk was of
the colour of sulphur.

EXPERIMENT VIZ..

COPPER.

To a bit of calico, which was immersed in a solu-
tion of acetite of copper in distilled water and dried
in the air, a few drops of the solution of carbon
were applied, but no visible change was produced.

On another bit of calico which was dipped in the
same solution of copper, some of the solution of car-
bon was dropped, the calico acquired a slight tinge
of brown ; it was kept wet with water, and in about
twenty minutes several white metallic films were
evident.

CHARCOAL. l°o

A bit of silk on which this experiment was made,
acquired a beautiful red colour, similar to the ruby
red with which copper tinges glass, and depending
on the same cause, viz. the quantity of oxygen com-
bined with the metal.

EXPERIMENT VIII.

LEAD.

A bit of white calico was immersed in a solution
of acetite of lead in distilled water and dried in the
air, then a few drops of the solution of carbon were
applied, but no visible alteration took place.

On another bit of the same calico, which was dip-
ped in the solution of carbon, a little of the same
solution of lead was dropped, and in a few seconds
films of reduced lead bright as silver appeared, the
calico was then immergcd in water, and transferred
a continuous pellicle of reduced lead to its surface.

This experiment was often repeated, both on silk
and calico •, sometimes the lead is reduced in an in-
stant, but at other times five or six seconds elapse
before any reduced lead becomes visible.

I also found that a solution of potash in alcohol
reduces lead ; but not so soon, or effectually, or in
Q2

186 REDUCTIONS BY

such quantity as the former solution does, but it is
evident, that these solutions differ only in the quan-
tity of carbon which they contain.

EXPERIMENT IX.

TIN.

To a bit of calico, which was immersed in a solu-
tion of muriate of tin in distilled water, and dried
in the air, some of the solution cf carbon was ap-
plied ; but no signs of reduction appeared, nor was
the colour of the calico much altered.

On another bit of calico which was dipped in the
solution of carbon, some of the same solution of tin
was dropped, a white precipitate was instantly form-
ed, attended with bright films of reduced tin ; the
calico was immerged in water, and left a bright me-
tallic film on the surface of that fluid.

The same experiment succeeds on silk.

EXPERIMENT X\

BISMUTH.

A piece of silk which was immersed in a solution
of nitrate of bismuth in distilled water and dried in

CHARCOAL. 187.

the air, suffered no visible alteration on applying the
solution of carbon.

• To a bit of calico which was clipped in the solution
of carbon, a few drops of the same solution of bis-
muth were applied, and immediately films of redu-
ced bismuth were evident. The calico was immer-
ged in water, and transferred a bright metallic film
to its surface.

This experiment succeeded also on silk-.

EXPERIMENT XI.

ARSENIC.

A bit of silk was immersed in a solution of mu-
riate of arsenic in distilled water and dried in the air,
then a little of the solution of carbon was dropped
on the silk, but no visible alteration took place.

Another bit of silk was dipped in the solution of
carbon, and when the alcohol evaporated, some drops
of the same solution of arsenic were applied ; and in
a short time a few minute metallic films were visible
on the silk, which when transferred to water, were
still more so.

188 REDUCTIONS BY

Tartrite of antimony treated in the same manner,
transferred a very delicate film, scarcely visible, to
the surface of water.

EXPERIMENT XII.

IRON.

A bit of calico which was dipped in a largely di-
luted solution of sulphate of iron, and dried in the
air, suffered no perceptible change on applying the
solution of carbon, except a slight tinge of brown.

Another bit of calico was immersed in the same
solution of iron, and placed on a bit of deal board,
a few drops of the solution of carbon were then ap-
plied, the calico was kept constantly wet with water,
and in about fifteen minutes films of reduced iron
were visible, the calico was immersed in water and
left a bright metallic film on its surface.

EXPERIMENT XIII.

ZINC.

To a bit of silk which was dipped in a largely di-
luted solution of muriate of zinc, and dried in the
air, a few drops of the solution of carbon were ap-

CHARCOAL. 189

plied, but scarce any alteration of colour, or other*
visible change occurred.

A piece of calico was immersed in the same solu-
tion of zinc, and placed on a bit of thin deal board,
a few drops of the solution of carbon were then ap-
plied, the calico was kept constantly wet with water,
and in about fifteen minutes films of reduced zinc
were evident ; the calico was immerged in water and
transferred a very bright metallic film of the colour
of zinc to its surface.

I also reduced muriate of cobalt in this manned

EXPERIMENT XIV\

MANGANESE.

To a bit of silk which was dipped in a diluted so-
lution of nitrate of manganese, and dried in the air,
some drops of the solution of carbon were applied,
but nothing appeared except a brown stain.

Another bit of silk was immersed in the solution
of carbon, when the alcohol evaporated, a few drops
of the same solution of manganese were applied ; a
brown stain was soon produced, the silk was kept wet
with water, and in about twenty minutes films of re-

190 REDUCTIONS BY

duced manganese of a bluish white colour were evi-
dent on the silk.

This experiment did not succeed with a strong so-
lution of nitrate of manganese.

The same experiment succeeds also on linen and
oalico, both with nitrate and sulphate of manganese,
the reduction is attended with violet and purple co-
lours, such as this metal imparts to glass and other
substances, in which it exists combined with different
proportions of oxygen; this difference is the cause
of the different colours which solutions of manga-
nese assume.

The bright films of reduced manganese soon dis-
appear, the cause ot which has been explained in
the first chapter of this essay ; the explanation there
offered is confirmed by the following facts.

" Regulus of manganese," says Mr. Bergman,
" when well fused, generally persists in a dry place,
" but sometimes undergoes spontaneous calcination,
" and falls down in a brownish black powder.

" Moisture, but particularly the access of aerial
" acid assists this operation. A small piece put into
" a dry bottle well corked, remained perfect for the
" space of six months, but afterwards exposed to the

CHARCOAL. 191

" open air of a chamber for two days, contracted a
» brownness on its surface, together with so much
« friability as to crumble between the fingers. The
« internal parts however, retained an obscure metal-
" lie splendour, which disappeared in a few hours."*

I shall now relate a few experiments made with
ether, alcohol, and gum.

EXPERIMENT XV.

GOLD.

I evaporated a solution of gold in nitro-muriatic
acid to dryness, and dissolved the salt in pure alco-
hol, the solution was poured into a phial carefully
dried in hot sand, and rinced with pure alcohol, the
solution filled about three-fourths of the phial, which
was carefully corked, and though it was nine months
exposed to the gray light, no films of reduced gold
appeared.

Part of the same solution was poured into a phial,
and diluted with water, films of reduced gold soon
appeared.

Chem. Essay, Vol. II. p. ao6 and 207, Eng. trans.

192 REDUCTIONS BT

-J&XPERIMENT XVI.

GOLD.

A phial half filled with a solution of gold in sul-
phuric ether was exposed nine months to the gray
light ; but no films of reduced gold were produced.

On a bit of silk, which was dipped in part of the
same solution of gold, and exposed to the gray light,
and kept wet with water, reduced gold appeared in
the space of a few hours.

EXPERIMENT XVII.

GOLD.

I mixed an aqueous solution of gold with a solution
of gum arabic in distilled water, in such proportion,
as to prevent the solution from spreading in the silk.

"With this solution I drew several stripes on a piece
of silk, and exposed it to the gray light of a chamber;
in some time the gold was reduced attended with blue
and purple colours.

CHARCOAL. 19S

Similar stripes were drawn on another piece of silk,
which, after the stripes became sufficiently dry, was
placed over the vapour of hot water ; and in about
fifteen minutes the gold was reduced in a beautiful
manner.

This solution was applied to another bit of silk,
which after it became sufficiently dry, was placed be-
tween the leaves of a blank book, to exclude the ac-
tion of light : the gold, after some time, was re-
duced.

I fc.und that small stripes and spots, made with
this solution, were reduced by breathing on them for
some time.

Sugar also, mixed with the solution of gold, pro-
motes the reduction ; but not so well as gum.

A bit of silk was dipped in a solution of nitrate of
silver in distilled water, and exposed, while wet, to
the sm >ke of a common fire ; in a short time reduced
silver appeared.

The following inferences are deducible from the
experiments related in this chapter.

I. Charcoal is capable of reducing the metals in
the ordinary temperature of the atmosphere.
R

194- REDUCTIONS BY

2. Water is essential to the reduction of metals by
charcoal : for these experiments prove, that the re-
duction cannot be effected without water.

3. Charcoal does not reduce the metals by giving
them phlogiston ; nor by uniting with and separating
their oxygen ; for were either of these opinions true,
metallic solutions in ether and alcohol, should be as
effectually reduced by charcoal, as metallic solutions
in water are.

4. Ether and alcohol do not promote the reduc-
tion of metals without the aid of water ; but when
this is present in sufficient quantity, they effect the
reduction, in the same manner, that charcoal and
other combustible bodies do.

It is evident then that charcoal reduces the metals
by decomposing water ; which seems to be effected
in the following manner.

The carbon of the charcoal attracts the oxygen of
the water, while the hydrogen of the latter unites in
its nascent state, with the oxygen of the metal, and
reduces it.

Hence it follows that the carbon is oxygenated by
the oxygen of the water, and forms carbonic acid,
while the metal is restored to its combustible state.

CHARCOAL. 195

This explanation is supported by the following
facts: M Gengembre has observed, that if charcoal
be im nersed in water, and kept at a temperature of
thirty degrees of the thermometer of M'. De Reau-
mur, the water is gradually decomposed, and inflam-
mable gas is formed.*

That charcoal effects the reduction of metals, in
high degrees of heat also, by decomposing water, is
evident from the following observations.

The great force with which charcoal attracts wa-
ter is a fatt sufficiently established ; Dr. Priestley is so
convinced of this, that he expresses himself in the
following strong terms. " I did not know, nor could
" believe the powerful attraction, that charcoal, or
« iron appear to have for water ; when they are in-
« intensely heated, they will find and attract it in the
« midst of the hottest fire through any pores in the
« retort."f

Now since water is essential to the reduction of me-
tals in low degrees of heat •, and since that fluid is
always present, when metals are reduced by charcoal
in high degrees of heat ; it is manifest, that charcoal
afts in the same manner in both these temperatures ;

* Essay en Phlogiston, new ed. by M. Kirwan, p. 6r.
f Ph. I. Trans. 1785. Vol. LXXV. p. sSo.

196 REDUCTIONS BY

and since water is easily, and instantly, decomposed
fay charcoal at a red heat, as the Antiphlogistiari9
themselves allow ; it clearly follows that their theory
of metallic reduction is erroneous : for since the wa-
ter is instantly decomposed by the charcoal, it is a ne-
cessary consequence, that its carbon must unite with
the oxygen of the water, while the hydrogen of the
latter unites in its nascent state, with the oxygen of
the metal, and reduces it, forming a new quantity of
water equal to that decomposed : this new quantity
of water may be decomposed in its turn : so that a
thimble full of water would be sufficient to reduce
any quantity of metal ; provided the water were pre-
vented from escaping, and time enough allowed.

Beside this source of water, the air of the atmos-
phere, which contributes to support the fire is an in-
exhaustible magazine of water : and the horter the air
is, the more water it holds in solution ; as M. Le
Roy has demonstrated.* Moreover all metallic oxids
and ores contain a large proportion of water.

From this view it appears, that the manner in-
which charcoal and other combustible bodies effect
the reduction of metals, is by assisting to decompose
water, the hydrogen of which is therefore the only
reducer of the metals.

* El. Nat. Hist. & Chem. Eng. Tr?.n~« in three volumes,
p. 163. Vol. I.

CHARCOAL.

197

Tn order to point out the difference between this
opinion and that of the Antiphlogistians, I shall pre-
sent the reader with M. Lavoisier's idea of metallic
reduction.

« It cannot be doubted," says that celebrated chy-
mist, " that charcoal at a red heat takes oxygen from
« all metallic substances ; this is a fact against which
" no exception can be made ; and it is the founda-
" tion of the whole theory of metallic reduction."

But the experiments in this essay demonstrate,
that this assertion is erroneous in every instance of
metallic reduction ; for, so far is it from being true,
that charcoal takes oxygen from all metallic substan-
ces •, it never does so in one single instance, since
its carbon always unites with the oxygen of the wa-
ter, the hydrogen of which unites immediately to
the oxygen of the metal, and reduces it.

« But this action or charcoal on oxygen," adds M.
Lavoisier, " this property, which it possesses of ta-
« king it from metallic substances, is not so strong in
" the cold, as at a red heat, since we are unacquaint-
« ed with any metallic revivification effefted by char-
" coal without heat."*

Essay on Phlog. a new ed. by M. Kirwan, p. 60,
R2

198 REDUCTIONS BY

It is evident that this mode of reasoning is no
longer of any weight, since charcoal does reduce
men is in the ordinary temperature of the atmos-
phere.

The reason charcoal is more powerful in high de-
grees of heat, than other reducers of the met?'.s, is
its great fixity in the fire, and the immense force
with which it attracts and imprisons water in its pores,
thus preventing its escape till it be decomposed by
an affinity, which is much more complex than has
been hitherto imagined.

Another reason of the superior power of charcoal
in metallic reduction is, that it forms a volatile elastic
fluid with the oxygen of the water, which flies off,
and consequently does not re-act on the metal, or
disturb, or impede by its presence, the action of the
reducing powers; advantages that phosphorus or any
other combustible substance, which forms a fixed
acid, that re-acts on the metal, can never possess.

LIGHT. 199

CHAPTER VIII.

REDUCTION OF METALS

BY

LIGHT.

THE next substance I shall treat of, is Light,
which seems well adapted to illustrate the theory of
metallic reduction ; as in experiments made with
this substance, water can be more effectually exclu-
ded, than in trials with any other reducer of the
metals.

Before any decisive experiments could be made on
light, or indeed any other reducer of the metals, it

200 KEDUCTIONS BY

is obvious that we should first ascertain the effects of
water itself in the ordinary temperature of the at-
mosphere-, to determine this point the two following
experiments were made.

EXPERIMENT I.

GOLD.

A piece of silk was immersed in an aqueous solu-
tion of nitro-muriate of gold, and suspended in a phial
over water i the phiai was corked, covered with black
silk, and placed in a dark closet to prevent the action
of light. The experiment was continued from the
20th of July to the 20th of October, during which
time the silk was frequently observed, and found to
continue moist, but no alteration could be perceived,
except that the yellow colour which the solution of
gold gave the silk, was changed to a light brown.

The silk was now taken out of the phial, and a
solution of phosphorus in ether applied to it; shortly
after, a white metallic film appeared; the silk was then
kept wet with water, and in some time reduced gold
of its proper colour appeared.

LIGHT. 20i

EXPERIMENT II.

SILVER.

A bit of silk which was dipped in an aqueous so-
lution of nitrate of silver, was suspended in a phial
over water, and placed in a dark closet from the 20th
of July to the 20th of October, and examined from
time to time, but **o alteration could be observed,
its white colour continued pure and unchanged.

The silk was now taken out of the phial, and the
silver was immediately reduced by means of a solu-
tion of phosphorus in ether.

Hence it appears, that water alone has not the
power of reducing, metals in the ordinary tempera-
ture of the atmosphere.

EXPERIMENT III.

GOLD.

On the 24th of July a piece of silk was immersed
in a solution of nitro- muriate of gold in water, and
dried by a gentle heat; it was then suspended in a

202 REDUCTIONS BY

window exposed to the sunbeams as much as possi-
ble ; no cha-ige was perceived on it till the 26th,
when the margin of the silk began to assume a pur-
ple tinge, which increased gradually, and on the
29th exhibited a few obscure specks of reduced gold
on the side of the silk opposed to the light.

The purple tinge continued to increase, and the
yellow which the solution of gold gave the silk de-
creased gradually, till on the 27th of August the co-
lour was a mixture of purple and light brown.

The reduction of the gold seemed to keep pace
with these changes of colour, and was very evident
on some parts of the silk even in the gray light, but
much more so in sunshine •, these changes were ob-
served till the 20th of October ; the experiment was
then discontinued, and scarce any reduced gold could
be seen on the side of the silk not opposed to the
light.

That this slight reduction of the gold and changes
of colour in the silk, depended on water absorbed
fro.n the air of the chamber, will appear from the
following experiments.

LIGHT. 203

EXPERIMENT IV.

GOLD.

A bit of silk which was dipped in the solution of
gold employed in the preceding experiment was dried
and suspended in a chrystal phial over dry carbonate
•f potash; the phial was then corked, and further
secured from external humidity by covering the cork
with wax: it was now placed in a dark closet twenty-
four hours, that the carbonate of potash might have
sufficient time to attract all the moisture it could from
the air of the phial, before exposing it to the action
of light.

The phial was then placed in a window exposed as
much as possible to the solar light, from the 24th of
July to the 20th of October, and carefully observed;
the same side of the silk was always opposed to the
light, and had the yellow tinge, which the solution
of ^old gave, altered to a brownish yellow : but the
oiher side of the silk suffered no visible change what-
ever, nor could any purple tint, or the smallest ves-
tige of reduced gold be perceived.

Another bit of silk which was immersed in the
same solution of gold and dried by a gentle heat,

204* REDUCTIONS BY

was suspended over some dry carbonate of potash,
contained in a chrystal phial covered with biack silk,
and placed in a dark closet during the same space of
time, but underwent no visible change whatever.

Both these bits of silk were now taken out of the
phials, and the gold was instantly restored to its me-
tallic splendour by means of water and a solution of
phosphorus in ether; a proof that the nitro-muriate
of gold in these bits of silk, suffered no change during
that space of time.

EXPERIMENT V.

GOLD.

A piece of silk, which was dipped in the same so-
lution of gold, and placed on a china plate exposed
to the sunbeams, was kept moderately wet with wa-
ter during the experiment; the first alteration obser-
ved was, that the yellow colour of the silk began to
change to a faint green, succeeded by a purple tinge,
which in about fifteen minutes exhibited some parti-
cles of reduced gold ; soon after the threads of the
silk, which acquired this purple tint were gilded

with j/old ; and, in about an hour, the who'e of the

1
silk was covered with a superb coat o r reduced gold,

exhibiting the texture of the silk in a beautiful man-
ner.

LIGHT. 203

i he purple tinge, which attended the reduction,
verged in some parts on red, and in others on blue.

This experiment, which is very amusing, I have re-
peated times unnumbered ; and when the sun is pow-
erful, and the solution of gold properly prepared and
of due strength, the coat of reduced gold is so bright
and dazzling, as to distress the eye of the beholder.

I find that the best way of preparing a solution of
gold for this purpose, is to separate the oxid of gold
from its solution in nitro-muriatic acid by means of
good ether.

The silk may be dipped in this solution, and when
the ether evaporates, kept moderately wet with dis-
tilled water.

It was with this solution in ether that I first re-
duced gold in the fibres of silk, and it was by means
of the same I discovered, that water was a necessary
condition in these reductions by light.

EXPERIMENT VI.

GOLD.

A bit of silk, which was dipped in a solution of ni-
tro-muriate of gold on alcohol, and placed in a china
S

206 REDUCTIONS BY

saucer exposed to the sunbeams, was kept vet with
alcohol for the space of an hour, but no change
even in the colour, which the solution of gold gave
the silk, could be perceived.

The alcohol diffused the solution of gold unequally
through the silk, the rays of the sun being intercept-
ed, suspended the experiment ; there was no sunshine
on the following day : on the third day the silk was
again exposed to the sunbeams, and kept wet with
alcohol, which extracted a yellow tincture ; a proof
that the gold in the silk suffered no degree of reduc-
tion ; the sun shone pretty strong for an hour or
more, and at length a faint tinge of purple, followed
by some reduced gold, appeared.

The preceding experiments leave us no room to
doubt that the purple tinge, and the small quantity
of reduced gold, that appeared in this experiment,
depended on water attracted from the air, or deposit-
ed in the silk by the alcohol during its evaporation.

Mr. Scheele reduced a solution of nitro-muriate of
gold in water by exposing it in a phial for a fortnight
to the rays of the sun.*

* Experiments on Air and Fire. Eng. Tranc. p. Zz.

LIGHT. 207

Mr. Lewis also made many experiments on the
Staining of marble, and other substances with metallic
solutions, and light.f

EXPERIMENT VII.

SILVER.

A piece of silk, which was immersed in a solution
©f nitrate of silver in water, was dried by a gentle
heat, and exposed to the light of the sun as much as
possible, in the window of a chamber from the 20th
of July to the 20th of October.

In less than an hour the silk acquired a reddish
brown colour ; next day the colour became more in*
tense and gradually increased, till on the third day
it bordered on black, which increased slowly -, at
length part of it became gray, and a few minute par-
ticles of reduced silver could be distinguished ; the
black tinge gradually disappeared, and the silk was
of a reddish brown colour ; the reduced silver had a
gray cast.

The following experiments demonstrate, that the
changes of colour and the few particles of semi-re-
duced silver, depended on water attracted from the
atmosphere.

-f- Commerce of the Arts.

208 REDUCTIONS BTf

EXPERIMENT VIII.

SILVER.

A bit of silk was immersed in part of the same so-
lution of nitrate of silver in water, and dried in the
dark, the silk retained its white colour ; it was then
suspended over dry carbonate of potash in a chrystal
phial, which was corked and secured from the in-
gress of moisture by covering the cork with wax.

The phial was left in a dark closet twenty-four
hours, that the salt might imbibe as much moisture
as possible from the silk and air.

The phial was then placed in a window, exposed
as much as possible to the rays of the sun, from the
24th of July to the 20th of October ; the silk scarcely
suffered any visible change, except a very faint tinge of
reddish brown, which was best seen by transmitted
light ; for the silk viewed by reflected light appeared
nearly white ; but that even this tinge, slight as it
was, depended on a minute quantity of moisture,
which the carbonate of potash was unable to extract,
appears from the next experiment.

LIGHT. 209

EXPERIMENT IX.

SILVER.

A piece of silk was dipped in a solution of fused
nitrate of silver in alcohol and carefully dried ; it was
then suspended over a quantity of concentrated sul*
phuric acid in a chrystal phial, which was coated with
a double fold of black paper and gum arabic, reach-
ing somewhat above the level of the acid to prevent
the light from acting on it ; the phial was corked^
and to exclude moisture more effectually, the cork
was covered with wax.

The phial was now placed in a dark closet twenty-
four hours, that the humidity of the enclosed silk and
air might be attracted by the acid ; it was then placed
in a window, exposed as much as possible to the rays
of the sun, from the 19th of July to the 26th of
October, but the silk underwent no visible change
whatever ; its white colour remained pure and unal-
tered.

The silk at the end of this period was taken out
of the phial, and wetted with water, a solution of
S 2

5210 REDUCTIONS "BY

phosphorus in ether was then applied to it, and in-
stantly the metallic splendour of the silver appear-
ed,

Another bit of silk which was immersed in a solu-
tion of nitrate of silver in water, and dried in the
dark, was suspended over dry carbonate of potash in
a phial, and placed in a dark closet about two months ;
the siik underwent no visible alteration whatever 5
its white colour remained pure.

I was desirous of knowing if the nitrate of silver in
this bit of silk suffered any change, that might ren-
der it incapable of reduction ; I therefore took it out
of the phial, and divided it into two parts ; one of
these was wetted with water, and the silver was in-
stantly reduced by a solution of phosphorus in ether.
The other part, which was suspended in a window,
exposed to the air of the chamber and rays of the
sun, soon acquired a reddish brown colour.

Hence it is evident, that these changes of colour
indicate partial reductions of the metal, and that they
never happen without the presence of water.

i-IGHT. 2 1 1

ERIMENT X.

SILVER.

A bit of silk, which was dipped in a solution of
nitrate of silver in water, was placed on a China sau-
cer, exposed to the rays of the sun, and kept mode-
rately wet with water •, in a few minutes the white co-
lour of the silk was changed to a reddish brown,
which by degrees became darker, and in about three
or four hours, though the solar rays were often lan-
guid and intercepted, acquired a blackish gray co-
lour, most of the reddish brown having disappeared;
next day there was no sunshine, but towards the
evening, particles of reduced silver were visible on
the side of the silk opposed to the light.

EXPERIMENT XI.

SILVER.

A bit of silk, which was immersed in a solution of
nitrate of silver in alcohol, and exposed to the beams
of the sun, as in the preceding experiment, was kept
moderately wet with alcohol, but resisted the action
of the light much longer than the preceding ; how-
ever in some time, specks and lines of a reddish
brown began to appear on some parts of the silk ;

212 REDUCTIONS BY

nexi day, though there was no sunshine, the reddish
brown colour increased a little; on the third day it
became more intense, but no black, or gray colour,
or particle of reduced silver, could be observed.

Whoever compares this with the preceding expe-
riments, can have no doubt that the changes of co-
lour which appeared in this experiment, depended
on water attracted from the air, or deposited in the
silk by the alcohol during its evaporation.

The experiments detailed in this chapter, prove
beyond the power of contradiction,

1. That water is essential to the reduction of me-
tals by light ; for these experiments demonstrate that
the reduction cannot take place without water, and
that it is always in proportion to the quantity of that
fluid present.

2. That light does not reduce metals by giving
them phlogiston, as Messrs. Macquer and Scheele
supposed ; for was this opinion true, light should
reduce them without the aid of water, and as well
with alcohol as with water.

3. Light does not reduce metals by fusing and ex-
pelling their oxygen, as the Antiphlogistians imagine;
for were this its mode of agency, the reduction
should happen without the assistance of water, and
as well with alcohol as with water.

LIGHT. 213

4. Light is a combustible body, for it acts like hy-
drogen, phosphorus, sulphur, and charcoal, in the
reduction of metals.

Since water then is essential to the reduction of
metals by light, and since light does not reduce me-
tals by giving them phlogiston, nor by fusing and ex-
pelling their oxygen, it follows, that the water is ei-
ther decomposed, or that it unites with metallic earths,
and constitutes their phlogiston, or that it unites
with and separates their oxygenous principle; but as
the two last suppositions are inadmissible, it is ob-
vious that light reduces the metals by decomposing
water.

After explaining the manner in which other com-
bustible bodies reduce the metals by decomposing wa-
ter, it will not be difficult to explain how light too
produces the same effect.

But in order to facilitate the explanation, it must
be premised,

1. That it is a law of attraction, that when any
body is deprived to a certain degree, of another, for
which it has a strong affinity, the attraction of the
former for the latter is much increased.

2. That light has a strong attraction for oxygen,
or the base of vital air.

214? REDUCTIONS BY

3. That when oxygen is condensed, and fixed in
any substance, it contains much less light and caloric
than it does in the gaseous state.

4. That the oxygenous principle exists in water in
this condensed state, and consequently has a strong
attraction for light.

Therefore when light reduces the metals, it at-
tracts the oxygen of the water, while the hydrogen
of the latter unites in its nascent state to the oxygen
of the metal and reduces it, forming at the same
time a quantity of water equal to that decomposed.

Hence it follows that the light is oxygenated and
changed into vital air, while the metal is restored to
Its combustible state.

ACIDS. 2J. r >

CHAPTER IX.

REDUCTION OF METALS

BY

ACIDS.

IT is well known that solutions of gold throw up
films of the reduced metal to the surface of the
fluid, and sides of the phials that contain them.

It has been shewn in the seventh chapter, that
this erFett depends on the presence of water, which
is further illustrated by the following experiments^

2,16 REDUCTIONS BY

EXPERIMENT I.

SILVER.

A drachm of saturated solution of nitrate of silver
in distilled water was mixed with half an ounce of
vinegar, in a few minutes a precipitate was formed ;
the whole was then poured on a filter and washed
with distilled water ; the precipitate acquired a bluish
gray metallic appearance ; the liquor which passed
the filter, got a brown colour and became blackish ;
next day bright films of reduced silver floated on the
liquor, and in some months after, a considerable part
of the inner surface of the phial was coated with re-
duced silver. Distilled vinegar did not produce this
effeft.

EXPERIMENT II.

PLATINA.

If a solution of the ore of platina in nitro-muriatic
acid be evaporated to dryness, and the salt dissolved
in water, films of a livid white metallic appearance
are thrown up to the surface.

ACIDS.

217

EXPERIMENT III.

TIN.

Some tin, which was dissolved in a china cup in
muriatic acid and evaporated to dryness, was dissol»
ved in distilled water-, immediately white metallic
iilms appeared on the surface of the liquor, and after
some hours, the whole surface of the solution was
covered with a continuous metallic pellicle, which
reflected all the colours of the rainbow, in a beauti-
ful manner.

EXPERIMENT IV.

MERCURY.

Mr. Bergman says, " calcined mercury is reduced
«* by digestion in acid of salt ; but the cause has not
« yet been sufficiently explored."*

As this reduction of mercury by muriatic acid is
doubted of by some, I made the following experi-
ment.

* Eleftive Attra&!ori5, Eng. trans, p. 223.

T

318 REDUCTIONS B7

A quantity of precipitate per se was put into a chi-
na cup placed on hot sand, and some muriatic acid
was poured on it •, the oxid was gradually dissolved,
and the digestion continued till the acid was nearly
evaporated, some distilled water was then poured on
.the salt, and minute films of a bright metallic ap-
pearance floated on the surface.

A nitrate of mercury was evaporated to dryness j
the salt acquired a slight tinge of yellow ; the cup
"was removed from the hot sand, and some water
poured on the salt ; immediately bright films of re-
duced mercury appeared, and in about three or four
hours the whole surface of the solution was covered
with a metallic pellicle, parts of which had the co-
lour and splendour of the metal, and other parts re-
flected a wonderful variety of the most beautiful ca-
lours.

EXPERIMENT V".

ARSENIC.

A quantity of white oxid of arsenic and muri-
atic acid was digested in the same manner in a chi-
na cup, a smart heat was continued till most of
the acid evaporated and left behind a mass of the
^consistence of tar, the surface of which had a gray

ACIDS. 219

appearance; after it cooled, some distilled water was
poured on, it diffused a disagreeable smell, and films
of reduced arsenic were thrown up to the surface ;
these were for some time remarkably bright, but
soon became of a dull gray colour, owing to the ra-
pid tendency of this metal to spontaneous calcina-
fion.

EXPERIMENT Vi,

MANGANESE.

Some concentrated sulphuric acid was poured ou

a auantit-v nf *u~ i- 1 - ' * * "
na cup, placed on hot sand; an effervescence was vi-
sible, but no sulphurous acid gas was exhaled ; the
cup was removed from the sand, before any percep-
tible quantity of the acid evaporated ; then some wa-
ter was poured on the mixture, and instantly the
surface of the fluid was covered with very brilliant
metallic films, and at the same time the solution ac-
quired a rose colour.

Some of the same oxid of manganese was dissol-
ved in nitric acid, in which a bit of sugar was put,
the solution was poured into a china cup placed on
hot sand, and as the evaporation proceeded, bright
metallic films appeared on the surface

220 REDUCTIONS BY

Mr. Bindheim of Moscow relates, that he reduced
the aerated calx of manganese dissolved in nitrous
acid; " the solution was placed upon an open fire in
" a glass retort."*

Happening to pour out a very largely diluted solu-
tion of sulphate of iron, I was surprised to find the
flags of the court in an hour or two after, covered
with large films of a livid white metallic aspect, these
films after the water evaporated, remained on the
flags several days.

In consequence of this I poured a largely diluted

solution of sulphate of iron into several shallow ves-

' .\~,~ f->*™ A f Vi"' r & r(J of the solution
covered with abundance or bright metallic hlms.

I also found that a largely diluted solution of mu>
tiate of zinc throws up bright metallic films to the
surface.

The reduction of metals by acids is a very convin-
cing proof of the decomposition of water, and seems
inexplicable on any other principle.

The reduction and calcination of metals by heat
and electricity are naturally explained on the same

• Crell's Chem. Journal, Vol. II. p. 48, Eng. trans',

ACIDS.

221

principle ; Dr. Priestley informs us in his History of
Electricity, Vol. I. p. 344, that S. Beccaria revived
several of the metals by the electric shock. It is
obvious that the electric fluid produces this effect in
the same manner, that other combustible bodies do,
viz. by decomposing water. When the red oxid of
mercury is reduced in close vessels by heat, the lat-
ter attracts the oxygen of the water, contained both
in the oxid and in the air of the vessels, while the
hydrogen of the water unites to the oxygen of the
mercury, reduces it, and forms a quantity of water
equal to that decomposed.

It is found, that if light and caloric act both at the
same time, the reduction is effected with more facility
than if either acted separately ; in this case, the su-
perior efficacy of the combined action of light and
caloric resembles that of other compound reducers of
the metals ; as that of sulphurated hydrogen gas,
phosphorated hydrogen gas, alkaline sulphure, &c.
which are more powerful than simple hydrogen gas,
sulphur, or phosphorus.

This superior efficacy of compound reducers, is
similar to what happens with some other combina-
tions of combustible bodies, as pyrites, pyrophori, a
mixture of lead and tin, &c. which have a more pow-
erful attraction for oxygen, than any of their ingre-
dients in a separate state.
T2

222 REDUCTIONS BY ACIDS.

Other acids, as the gallic, the tartarous, the formic,
&c. and also alkalis, as ammonia and soda, hare the
power of reducing some of the metals, fads well
known to chyraists.

OXYGENATION. 223

CHAPTER X,

OXYGENATION

OF

COMBUSTIBLE BODIES-.

IT has been shewn, in the preceding chaptefs>
that water is essential to the reduction of metals; that
it is always decomposed in that process, and that the
reducing substances are oxygenated by the oxygen of
the water, while the hydrogen of the latter reduces
the metals.

That water is also decomposed in every instance of
oxygenation, and that the oxygen of water alone

%2£ ©XYCENAT10N.

oxygenates combustible bodies will appear from the
following observations.

AZOTE.

The first case of oxygenation, we shall consider,
is that of Azote, in an experiment of Dr. Priestley,
which has been urged by Mr. Kirwan with great suc-
cess against the Antiphlogistians.

** If the electric spark be taken in nitrous air, it
•will be reduced to one- third of its bulk, and the resi-
duum is mere phlogisticated air, and a little acid is
deposited. Now the Antiphlogistians own that ni-
trous air contains both pure air and phlogisticated air;
since therefore this pure air disappears, is it not evi-
dent that it was converted into water? and since the
formation of water requires the presence of inflam-
mable air, does it not follow that the nitrous air con-
tained this also ?"*

To this objection M. Berthollet replies, that the
diminution of the nitrous gas " is owing to the com-
bination of the mercury with the oxygen, which ex-
isted in the gas."f

* Essay on Phlogiston, new Ed. p. it*.
j* Ibid. p. 122,

OXYGENATION. 225

But this answer is insufficient, as it does not ac-
count for the water and acid that appeared ; and in-
deed by this experiment, the Antiphlogistians are
refuted on their own principles, and the decomposi-
tion of water is incontestably proved ; for as nitrous
acid could not be formed without more oxygen than
what existed in the nitrous air, is it not evident that
this oxygen must be derived from the water contain-
ed in the nitrous air ? It is obvious then, that the wa-
ter of the gas was decomposed, which seems to have
been effected in the following manner.

The ele&ric spark diminishes the attraction of the
constituent principles of the water for each other ;
hence the azote of the gas unites with the oxygen of

u:t<v fKo hvdrogen of the latter combines

with the oxygen of the gas; ana mus waici «iuu ni-
trous acid are formed.

The formation of nitrous acid in Mr. Cavendish's
noted experiment, cannot be explained on any other
principle than the decomposition of water : when the
cle&ric spark is taken in a mixture of azotic gas and
vital air, the water of these airs is decomposed; the
electric flame lessens the force with which the oxy-
gen and hydrogen of the water adhere ; hence the
azote seizes the oxygen of the water and forms ni-
trous acid, while the hydrogen of the water unites
with the oxygen of the vital air, and forms a quan-
tity of water equal to that decomposed.

226 OXYGENATION.

When nitrous and vital air are mixed, the whole
mass " hisses, turns red, grows warm, and contracts
in bulk," the azote of the nitrous air attracts the
oxygen of the water and forms nitrous acid, while
the hydrogen of the water unites in its nascent state
with the oxygen of the vital air, and forms a quan-
tity of water equal to that decomposed.

Hence while the azote of the nitrous air is oxy-
genated, the caloric is restored to its combustible
state.

" But it is to be observed," says M. Bergman,

treating of this experiment, " that the decomposition

of nitrous air is the effect of a double attraction ; the

phlogiston is attracted by thf « : — ' ' *

pan toy sue water. Therefore, when the mixture is

made in a phial immersed in mercury, the experi-
ment fails."*

HYDROGEN.

The combustion of hydrogen gas with vital air is
explicable only on the decomposition of the water
contained in these airs -, thus when flame, or a glowing
body is applied to a mixture of them, the attraction
of the principles of the water for each other is dimi-

* Elec. A«r. Eng, Trans, p. an.

OXYGENATION. 22*/

riislied ; therefore the hydrogen of the inflammable
air unites with the oxygen of the water, while the
hydrogen of the latter seizes the oxygen of the vital
air ; thus the whole bulk of the airs which are changed
into water disappears, and their light and caloric are
restored to the combustible state.

Hence it appears that water is not formed during
the combustion of vital and inflammable air, in the
manner the Antiphlogistians suppose.

Indeed it is obvious, that if these airs contained no
water they could never be burned ; for since they
are already saturated with light and caloric, they can
have no attraction for any additional quantity of
these fluids ; and consequently can suffer no other
change from the light or caloric of a glowing body
than a greater degree of expansion, and therefore
could never unite.

The same reasoning applies to the combustion of
all elastic fluids.

PHOSPHORUS,

Vital air always contains a large proportion of wa-
ter ; when phosphorus is burned in this air it attracts
the oxygen of the water, and forms phosphoric acid,
while the hydrogen of the water unites with the

228 OXYGENATION.

oxygen of the gas, and forms water which unites with
the acid.

Hence the weight of the acid formed is equal to
the weights of the oxygen gas and phosphorus con-
sumed ; and the light and caloric, which appear du-
ring the combustion are restored to their combusti-
ble state.

This explanation is confirmed by an observation
of Mr. Bergman, who says,

" In vital air, without the aid of external heat,
phosphorus is consumed very slowly, and scarce at all
unless water be present."*

Therefore the phosphorus does not unite to the
oxygen of the vital air as M. Lavoisier supposes, but
to the oxygen of the water contained in the oxygen
gas.

SULPHUR.

When sulphur is burned in vital air it attracts the
oxygen of the water and forms sulphuric acid, while
the hydrogen of the water attracts the oxygen of the
gas, and forms a quantity of water equal to that de-

* El. Att. Eng. Trans, p. 213.

OXYGENATION 229

composed : the light and caloric are at the same time
restored to their combustible state.

The sulphur then does not unite with the oxygen
of the vital air as the Antiphlogistians imagine, but
with the oxygen of the water contained in that gas.

CHARCOAL.

In like manner during the combustion of charcoal
in vital air, the carbon attracts the oxygen of the
water, and forms carbonic acid, while the hydrogen
of the water unites with the oxygen of the vital air,
and forms a new quantity of water equal to that de-
composed.

Hence the carbon of the charcoal does not unite
with the oxygen of the vital air as M. Lavoisier sup-
poses, but with the oxygen of the water contained
in that gas.

That water is decomposed in every instance of
combustion, is further proved by attending to what
passes during the burning of a common fire ; the
carbon of the fuel combines with the oxygen of the
water and forms carbonic acid, while the hydrogen
of the water unites partly with the oxygen, and partly
with the azote of the atmosphere, and forms water,
and the ammonia which abounds in soot.
U

2ii0 OXYGENATION.

From these observations it is evident, that lM.
Lavoisier's account of the formation of water and
acids is erroneous, and inadequate to explain the

phenomena.

The different kinds of fermentation are so many
instances of the decomposition of water ; in every
case of them, combustible bodies are oxygenated by
the oxygen of the water, while others are restored
by ijs hydrogen to their combustible state.

Hence the azote, ammonia, and carbonic acid of
fermentation, the inflammable air of marshes, mines,
&c. — the azotic and hydrogen gases ascend into the
atmosphere, and there meeting the vital air discharged
from the water of plants, &c. form neiv quantities
of air and water.

When the azote is oxygenated, it unites with the
oxygen of the water contained in the air and forms
atmospheric air, and sometimes perhaps nitrous acid ;
the hydrogen of the water combines at the same
time with the oxygen of the vital aij:, and forms a
quantity of water equal to that decomposed.

But when the hydrogen is oxygenated, a quantity
of water double that decomposed is regenerated ; for
the hydrogen of the gas unites with the oxygen of
the water, while the hydrogen of the latter seizes the

OXYGENATION. 231

oxygon of the vital air ; and thus a quantity of wa-
ter double that decomposed is formed, and that part
of it which the atmosphere cannot suspend descends
in the form of rain.

When these decompositions arc rapid, the pheno-
mena of thunder and lightning appear.

This account of the renovation of our atmosphere
explains why the phenomena of thunder and light-
ning appear sometimes with, and sometimes without
rain ; and also accounts for the production of the ni-
trous acid, which Mr. Margraaf discovered in the
purest snow.

The breathing of fishes is a striking proof of the
decomposition of water in respiration.

For this view of the formation of our atmosphere-
I am indebted to a friend well acquainted with the
experiments related in this essay, and also for the
application of the opinion which I venture to ad-
vance to the respiration of animals.

The phenomena of vegetation cannot be explained
on any other principle, than the decomposition of
water by heat and light, which uniting to the o::y-
gen of the water contained in vegetables, change it
into streams of vital air that serve to renovate our

26& OXYGENATION-.

atmosphere ; the hydrogen of the water at the same
time contributes to form the oil and other principles
of plants, and when these are decomposed by the
various processes of combustion, forms a quantity of*
water equal to that consumed in their formation.

The changes, which nitric acid suffers by expo-
sure to heat or light, are explained with ease on this
principle ; the light unites with the oxygen of the
water contained in the nitric acid and forms vital air s
while the hydrogen of the water combines with the
oxygen of the acid, and forms a new quantity of wa-
ter equal to that decomposed ; thus the nitric is con-
verted into the ruddy nitrous acid.

METALS.

According to the Antiphlogistians, " In every me-
tallic solution by an acid, the metal in order to be-
come oxided, decomposes either the acid itself or the
water of solution, or it obtains from the atmosphere
the requisite quantity of oxygene. In the second case,
hydrogenous gas in a state of greater or less purity
is disengaged, and the acid remains entire without
decomposition, which is proved by the quantity of
alkali necessary to saturate it. In the first case, one of
the principles of the acid, or the acid deprived of part
of its oxygene is disengaged and fused in the caloric,
which is separated at the same time j such are ni-

OXYGENATION. 233

Irous gas and sulphurous acid gas. In the third case,
neither the water nor the acid are changed ; such Ls
the solution of copper by the 2cetous acid.

" The muriatic acid and. the vegetable acids,
which are formed of radicals, or acidifiable princi-
ples, which have more affinity with oxygene than the
metals have, are not decomposed by these metals,
and the oxygene is always afforded to these last by
the water or atmosphere. Hence the solutions by
these acids afford only hydrogenous gas, or do not
effervesce at all.

" There are some cases in which the water and
the acid, are at the same time decomposed by the
metal, as in the solution of tin in the nitric acid, ac-
cording to the observation of M. De Morveau.

" Tin is so greedy of oxygene, and requires so large
a quantity for its saturation, that after having absorb-
ed that of the nitric acid, and reduced it to the state
of azote, it decomposes likewise the water, and dis-
engages hydrogen. These two principles being sepa-
rated from their first compounds, unite together and
immediately form ammoniac. Hence there is no dis-
engagement cf elastic fluid. In this case it appears,
that the formation of ammoniac, in the solution of
tin by the nitric acid always takes place ; for by
throwing quicklime or caustic fixed alkali into this
TT2

234- OXYGENATION.

solution, there is always a disengagement of ammo-
niac."*

It is evident then that this account of the oxyge-
nation of metals, given by the Antiphlogistians, is
equally complex as their account of metallic reduc-
tion, and improbable ; since every case, in which
they deny the decomposition of water, and derive
the oxygen from other sources, is easily and naturally
explained on that principle, as will appear from what
follows.

Thus when mercury or silver is dissolved in nitric
a'cid, the metal attracts the oxygen of the water,
while the hydrogen of the latter unites with and se-
parates more or less of the oxygen of the acid, which
is thus changed into nitrous air.

The same thing happens during the solution of
other metals in this acid, the only difference being
the greater or less energy and rapidity with which
they combine with the oxygen of the water.

This decomposition of water is confirmed by the
solution of tin in this acid, in which the Antiphlo-
gistians allow the decomposition of the acid, and the

* Essay on Phlog. new Ed. by Mr, Kirwan, p. 233— 23c.

OXYGENATION. 2 #5

water too, for ammonia is formed by pari & tne hy-
drogen of the water, and azote of the acid.

In every case of metallic solution by sulphuric and
muriatic acids, whether concentrated or diluted, wa-
ter is decomposed ; the metals attracting the oxygen
of the water, while its hydrogen escapes in the form
of inflammable air, or unites partly with the oxygen
of the acid, and partly with caloric; hence the vola-
tile sulphurous acid, and muriatic acid air obtained,
always contain some hydrogen gas, as appears from
the following observation of M. Bergman.

" By means of vitriolic acid, inflammable air fs
obtained from zinc and iron, as also by means of ma*
rine acid •, but from the other metals dissolved in vi-
triolic acid, we obtain another species of air, called
vitriolic acid air : and by the marine acid, another si-
milar to the former, called muriatic air, but both,
more o* less mixed with inflammable air"'

•*

Again, when copper is dissolved in the acetous
acid, the copper attracts the oxygen of the water,
while the hydrogen of the latter unites with the oxy-
gen of the atmosphere and forms water; hence no
effervescence appears.

» Chem. Essays, Vol, II. ?• 35*- Infr'WM.

236 OXYGENATION,

When alkalies dissolve metals, the latter are always
oxygenated at the expense of the water, which holds
the alkali in solution; thus when lead and copper are
dissolved, the metals combine with the oxygen of the
water, while its hydrogen unites to the oxygen of the
atmosphere and forms water ; hence no hydrogen
gas appears.

The oxygenation of metals and other substances
by heat and air is easily explained on the same prin-
ciple ; the metals, Sec. unite with the oxygen of the
water contained in atmospheric air, while the hydro-
gen of the water combines with the oxygen of the
air, and forms a quantity of water equal to that de-
composed.

This explanation is clearly proved by an experi-
ment of Mr. Bergman on the regulus of manganese,
which if kept in a dry place, retains its metallic
splendour, but if exposed to moisture, is soon oxyge-
nated, and loses its lustre.*

It is further confirmed by the authority of the
distinguished Mr. Scheele, who says that « the wa-
ter contained in common atmospheric air is the chief
cause of the ignition of pyrophorus," which he pro-
ved by the following experiment.

• Chem. Essays, Vol. II. p. ao6 and 207. X,ng, tu.rs -

OXYGENATION.

i.', off

" I made a very dry air by putting some very small
pieces of quicklime into a small matrass, then I put
the neck of another matrass into that of the first, so
that the air of both might communicate, and I luted
the crevices with wax. Two days afterwards I sepa-
rated the empty matrass, and poured half an ounce
of pyrophorus from my phial into it, and immediate-
ly carefully shut the aperture up ; but I did not ob-
serve that it grew in the least warm ; an hour after
this I put a sponge moistened in water into the ma-
trass, and shut it up again: a few minutes after the
pyrophorus began strongly to be heated, and some
pieces kindled spontaneously."*

Many other fa&s might be adduced to prove, that
oxygenation cannot take place without water, as the
combustion of mixtures of iron filings, sulphur and
water, of alksline sulphure and water, &c. in which
the water is decomposed, and the combustible bodies
oxygenated by its oxygen.

It is evident then from the experiments and obser-
vations related in this essay, that water is essential to
the oxygenation of combustible bodies, and that it is
the only source of the oxygen that oxygenates them:
it is also evident that when one body is oxygenated,

* Exp. on Air and Fire, Eng. nans. p. us and 130.

238 OXYGENATION.

another at least is restored to the combustible state:
hence it appears that the oxygenation of combustible
bodies is never effected by a single affinity.

The Antiphlogistians treating of the precipitation
of metals by each other say,

" Since the metals cannot remain united to the
acids, but in the state of oxides of a determinate de-
gree, it is easily conceived, that by plunging into a
metallic solution a metal which has a stronger affinity
with oxygenethan that which is dissolved, the former
must deprive the latter of its oxygene, take its place
in the acid, and cause the second to subside in a form
more or less metallic, accordingly as it has deprived
it of more or less oxygene. This is the reason of the
precipitation of silver by copper, copper by iron,"*
&c

But this account of the precipitation of metals by
one another cannot be admitted, for it has been pro-
ved in every instance of reduction related in this es-
say, that water is decomposed, and that its hydrogen,,
is the only substance that restores bodies to their
combustible state.

* Essay on Phlogiston, new edit, by Mr. Kir war., j). 236
and 237.

OXYGENATION. 239

There is no reason then to suppose that nature de-
viates in this particular case, from that uniform sim-
plicity, which she constantly observes in all her ope-
rations.

Therefore it is obvious, that when one metal pre-
cipitates another in a form more or less metallic, the
precipitant unites with the oxygen of the water, while
the hydrogen of the latter combines with and sepa-
rates the oxygen of the precipitated metal, and thus
reduces it.

The experiments made with phosphorus and me-
tallic solutions in ether, alcohol, and water, prove
the truth of this explanation, and shew that when
one metal precipitates another in the metallic form,
it a&s like a stick of phosphorus, decomposing the
water.

This account of the reduction of one metal by
another is supported by the opinion of Mr. Bergman,
who says,

« It is well known, that the calx of copper dissol-
ved in vitriolic acid is precipitated in its metallic form
on the addition of iron-, and that by means of a dou-
ble eleftive attraaion, for the iron dissolving in the
acid would form an inflammable air by its phlo-

€4-0 OXYGENATION".

giston, were not the copper present, which takes it
ap.' 5 *

The same author remarks, that a small excess of
acid is necessary, and that without it no precipitation
begins.

Now since water is decomposed by iron and sul-
phuric acid, it must be allowed, that when iron is
immersed in a solution of sulphate of copper, the
water is decomposed by the iron and excess of acid,
the iron attracting the oxygen of the water, while
the hydrogen of the latter unites to the oxygen of
the copper, reduces it, and forms a quantity of wa-
ter equal to that decomposed.

The precipitation of silver in its metallic form by
iron and other metals is to be explained in the same
manner, and not by a single affinity as the Antiphlo-
gistians imagine.

The reduction of gold and seme other metals, by
solutions of sulphate of iron and muriate of tin, is
readily accounted for on the principles advanced here;
for fresh made solutions of sulphate of iron and mu-
riate of tin contain hydrogen, and have the power of

Chem. Essays, Vo!. H. p. tf^, Eng. tia«s.

OXYGENATION. 241

decomposing water ; the oxygen of which unites
with the iron and tin, while its hydrogen seizes the
oxygen of the gold, &c. reduces it, and forms a
quantity of water equal to that decomposed.

The decomposition of water is further proved by
the large dilution necessary to form the arbor Dianae,
the purple precipitate of Cassius, and other instan-
ces of the reduction of metals by one another.*

* It appears impossible to explain, except by the play of
double affinity here pointed out, (by which the decomposition
of one substance is accompanied with the formation of an-
other,) the uniform state of the atmosphere at all times, and
in all places : without this wise provision, let us for a moment
consider the immense consumption of oxygen from the atmos-
pheric mass, by the constant processes of respiration from
one thousand million inhabitants of the globe; from at least
as many animals, and probably myriads of insecls, &c. which
all require their proportion of this vivifying element. To
these we mu->t add the consumption from domestic and vol-
canic fiies, from fermentation and other processes continually
going on in every region— and with these data, let us est. mate
the probable amount.

By Hale's experiments, a candle with a flame of half a cu-
bic inch, consumed per minute twenty-six cubic inches of air;
which by calculation amounts to about six hundred and fifty
nine cubic feet per annum. Now supposing each person, in
•respiration, to consume the same per annum, it will afford an
amount of six hundred and fifty nine thousand millions of
cubic feet ; as much for animals; probably as much for in-
sects • certainly as much for fires, candles, -and other sources

X

242 OXYGENATION.

of combustion ; and the same for every spec ; es of fermenta-
tive process; and we have the above amount five times multi-
plied, without extending the view to fish : or equal to three
billions, two hundred and ninety -five thousand millions of
cubic feet of pure air annually expended} to supply which,
nothing but the constant extiication of a similar quantity by
co-instantaneous operations, can be supposed adequate to keep
the atmosphere in the same uniform state of purity. This
apparently could not be the case, were atmospheric oxygen,
the sole, or even principal source of supply in these extensive
operations : and this view however imperfect, may serve to
corroborate the sentiments of the ingenious author.

Am. Ed,

CONCLUSION. 243

CHAPTER XI.

CONCLUSION,

I SHALL conclude with a general view of the
inferences, which I ventured to advance in this

essay.

1. Neither the Phlogistians nor Antiphlogistians
account in a satisfactory manner for the increase of
weight, which bodies acquire during combustion.

2. Their account of the formation of water, acids,
and oxids, is erroneous ; for it has been shewn that
the oxygen of water alone oxygenates combustible
bodies.

244 CONCLUSION.

3. Combustible bodies, as hydrogen, phosphorus,
sulphur, charcoal, light, &c. are capable of reducing
the metals in the ordinary temperature of the atmos-
phere ; and indeed I might add at a much lower
temperature, as I frequently experienced.

4. Combustible bodies do not reduce the metab
by giving them phlogiston, as the Phlogistians sup-
pose ; nor by uniting with and separating their oxy-
gen, as the Antiphlogistians maintain.

5. Water is essential both to the reduction and
oxygenation of bodies, and is always decomposed in
'hese operations.

6. Water does not contribute to metallic reduction
merely by dissolving and minutely dividing the par-
ticles of metallic salts, and thus removing the impe-
diment opposed to chymical attraction by the attrac-
tion of cohesion ; for were this the case, metallic so-
lutions in ether and alcohol, in which that impedi-
ment is equally removed, should be as readily and
effectually reduced as metallic solutions in wates
are.

This circumstance, in which all the experiments
on metallic reduction detailed in this essay exactly
coincide, merits particular attention, and shews that

CONCLUSION. 2$5

the manner, in which combustible bodies effect the
reduction, is the same in them all.

7. When one body is oxygenated, another at least,
is restored at the same time to its combustible state;
and vice versa when one body is restored to its com-
bustible state, another at least is at the same time
oxygenated.

8. Quantities of air and water, equal to those de-
composed in the different species of combustion, are
constantly forming.

Thus nature by maintaining this balance of power
between combustible and oxygenated bodies, pre-
vents the return of original chaos.

Since then in every act of combustion, one body at
least is oxygenated, and another restored at the same
time to its combustible state, the phenomena of com-
bustion may be referred to two heads, viz.

Oxygenation, or the union of oxygen with combus-
tible bodies, and

Reduclion, or the restoration of oxygenated bodiea-
to their combustible state.

And since in every instance of combustion water
is decomposed, and one body oxygenated by the

246 CONCLUSION.

oxygen of the water, while another is restored to its
combustible state by the hydrogen of the same fluid,
it follows,

1. That the hydrogen of water is the only sub-
stance, that restores bodies to their combustible state,

2. That water is the only source of the oxygen,
which oxygenates combustible bodies.

3. That no case of combustion is effected by a
single affinity.

This view of combustion may serve to shew how
nature is always the same, and maintains her equi-
librium by preserving the same quantities of air and
water on the surface of our globe •, for as fast as
these are consumed in the various processes of com-
bustion, equal quantities are formed, and rise rege-
nerated like the Phenix from her ashes.

NOMENCLATURE.

24tf

NOMENCLATURE OF CHYMICAL TERMS

USED IN THIS ESSAY.

.NEW NAMES.

Ammonia
Acetite of lead

copper

Azote (nitrogen)
Azotic gas
Alkaline sulphure
Alcohol

Carbon
Carbonic acid
Caloric
Hydrogen

gas

Hydrure of sulphur

_ . phosphorus

Muriate of tin

silver

arsenic

zinc

* cobalt

OLD NAMES.

Caustic volatile alkali.

Sugar of lead.

Verdigris.

Base of phlogisticated air.

Phlogisticated air.

Liver of sulphur.

Highly rectified spirit of

wine.
Pure coal.
Fixed air.
Heat.

Base of inflammable air.
Inflammable air.
A compound of hydrogen

and sulphur.
A compound of hydrogen

and phosphorus.
Salt of Jupiter.
Luna cornea.
Arsenic combined with

muriatic acid.
Marine salt of zinc.
Marine salt of cobalt

NOMENCLATURE.

NEW NAMES.

Nitric acid

Nitro-muriatic acid
Nitro-muriate of gold

Nitrate of silver

platina

Oxygen

mercury
bismuth
manganese

gas

OLD NAMES.

Dephlogisticated nitrous

acid.
Aqua regia.
A compound of gold and

aqua regia.
A compound of platina and

aqua regia.
Lunar nitre, chrystals o-f

the moon.
Mercurial nitre.
Nitre of bismuth.

Oxygenated muriate of

mercury.
Prussiate of mercury

Phosphorated hydrogen

gas
Potash

Sulphuric ether
Sulphureous acid gas
Sulphurated hydrogen gas
Sulphate of copper

— — i iron

manganese

Soda

Tartrite of antimony

manganese.

Base of vital air.
Vital air.
Corrosive sublimate.

A compound of mercury

and prussic acid.
Phosphoric air.

Caustic vegetable alkali.

Vitriolic ether.

Volatile sulphureous acid.

Hepatic air.

Blue vitriol.

White do

Green do.

Vitriol of manganese.

Caustic mineral alkali.

Emetic tartar.

THE END.

• * ARMY * *
MEDICAL LIBRARY

Cleveland Branch